To get the economy back on track, China is trying to champion its domestic companies and reassure entrepreneurs that it’s ready for business.

Its efforts are running into a problem: an online army of Chinese nationalists who have taken it upon themselves to punish perceived insults to the country — including from some of China’s leading business figures.

In recent weeks, bloggers who usually rail against the United States have turned on China’s richest man, calling him unpatriotic, and encouraged boycotts that have wiped out billions from his beverage company’s market value. When fellow tycoons defended him, they were attacked as well, by users whose profiles featured photos of the Chinese flag.

As the fervor spread, social media users also hounded Huawei, the crown jewel of China’s tech industry, accusing it of secretly admiring Japan. Others accused a prestigious university of being too cozy with the United States, and demanded the works of a Nobel-winning Chinese author be removed from circulation for purportedly smearing national heroes.

The state has often encouraged such nationalist crusaders, deploying them to drum up support, deflect foreign criticism or distract from crises. Social media users have suggested that the coronavirus originated in an American lab, and staged boycotts against Western companies that criticized China’s human rights record. Self-styled patriotic influencers have made careers out of criticizing foreign countries.

But the encouragement has also pushed many users to try and outdo one another in nationalist outrage — to an extent that can sometimes escape the government’s control or undercut its broader aims. As the recent attacks grew, some state media outlets issued rare rebukes of the nationalist bloggers. Hu Xijin, a former Communist Party newspaper editor who is perhaps the most well-known online nationalist, also condemned the craze. Yet the barrage persisted.

“While nationalism and populism are quite useful tools, they are pretty dangerous as well,” said Yaoyao Dai, a professor at the University of North Carolina at Charlotte who has studied Chinese populism. “The government needs and wants to be the one that shapes the narrative. They cannot just give everyone this power to shape the narrative of who are ‘the people’ and who is ‘the enemy.’”

This time, many of the grievances seem to be fueled by a groundswell of discontent over China’s economic malaise, potentially making it harder for the authorities to turn the faucet of public anger off.

Some of those calling for boycotts of the drinks company, for instance, suggested it was focused more on profits than on the public good, amid high youth unemployment and disaffection with harsh corporate culture.

The attacks on the beverage company, Nongfu Spring, and its billionaire owner, Zhong Shanshan, began last month after the death of the founder of a rival drinks company called Wahaha.

The Wahaha founder, Zong Qinghou, had built a reputation for not firing workers, and offering housing and child care subsidies. After his death, some users began comparing Mr. Zong with Mr. Zhong of Nongfu, and asking why the latter did not show the same generosity.

But the attacks soon spiraled far beyond his business practices. Critics pointed out that Mr. Zhong’s eldest son held American citizenship, and declared the family traitors. Others said that the design of one of Nongfu’s drinks seemed to evoke Japanese imagery — a cardinal sin to nationalists, given China’s fraught history with Japan.

Still others seized on the fact that Nongfu had overseas shareholders, accusing it of enriching foreigners at the expense of China.

“In this current environment, when most people can’t make much money, they’ll be in a bad place, and they’ll resent the rich,” Rebecca Fei, a 35-year-old resident of Hangzhou, the eastern Chinese city where both drinks companies are headquartered, said in an interview. Ms. Fei had published social media posts praising Wahaha’s work culture and criticizing Nongfu Spring.

Around the world, anti-elite sentiments often go hand-in-hand with economic downturns. But China’s tightly controlled internet incentivizes users to blend that sentiment with aggressive nationalism. With Chinese censors deeming more and more topics off-limits, pro-China sentiment is one of the few reliably “safe” areas remaining.

The allure of making incendiary clickbait may be even stronger now amid the shortage of well-paying jobs, said Kun He, a postdoctoral researcher at the University of Groningen in the Netherlands who studies China’s online populism. Some bloggers “take advantage of this populist sentiment to attract traffic for their own profit,” he said.

Online streamers began posting videos of themselves pouring Nongfu Spring water down the toilet. Several convenience stores declared that they would no longer stock its products. Nongfu’s stock value has fallen 8 percent since last month.

As the frenzy built, a state-owned newspaper in Hangzhou published an opinion piece calling on the public to treat entrepreneurs as “one of our own,” though it did not mention Nongfu Spring by name. The propaganda department of Zhejiang Province, of which Hangzhou is the capital, denounced bloggers who “damaged the normal economic order.”

The warnings had little effect. Other entrepreneurs who defended Nongfu found themselves attacked, too. Li Guoqing, the co-founder of Dangdang — once called China’s version of Amazon — urged social media users in a video to let businesspeople get back to business, only for commenters to point out that his son, too, was an American citizen. Mr. Li later deleted his video.

Nationalist furors often subside as quickly as they arise, and Mr. Zhong is still China’s richest person, with a net worth of over $60 billion. But the mania against Nongfu made clear how easily nationalists can descend upon targets other than those selected by the authorities.

Several more campaigns have recently taken aim at other storied institutions and figures, in spite of official efforts to dissuade them.

Some social media users have fumed that some graduates of Tsinghua University in Beijing, routinely ranked the country’s best, go on to study in the United States. They pledged not to send their own children there, even after a social media account tied to People’s Daily, the Communist Party mouthpiece, criticized the attacks as ill-founded.

Critics also rounded on Huawei, the tech giant, after a Weibo user posted that the company was suspicious, because it had named a line of chips Kirin, another unacceptable Japanese reference. The post, now deleted, appeared to be sarcastic. But as it went viral, some users earnestly took up the call to arms.

Then there was a man named Wu Wanzheng, who announced on Weibo last month that he had sued Mo Yan, the only Chinese national to win a Nobel in literature. Mr. Wu — whose social media username is Mao Xinghuo, in a nod to Mao Zedong — claimed that Mr. Mo had smeared the military and insulted Mao in his novels, which often depict the turbulence of 20th-century China. He requested that Mr. Mo’s books be removed from circulation.

Mr. Wu’s suit has not been taken up by a court, and his account on Douyin, the Chinese version of TikTok, was recently banned. Hashtags about his lawsuit, after trending on Weibo, were censored.

Still, the authorities were wielding a relatively light touch, compared to how vigorously they have worked to silence any criticisms of Beijing’s economic policies. Attacks on Mr. Mo have continued, including by Mr. Wu, who declined an interview request, and other bloggers like Zhao Junsheng, a 67-year-old retired state company worker.

Mr. Zhao, whose videos attacking Mr. Mo have racked up more than 15,000 likes, admitted he had not read any of his novels. But he was disgusted by the idea that people might criticize Mao-era China, when workers had been taken care of. That time was just as important as China’s modern-day market economy, he said in an interview.

“I think they must have foreign forces behind them,” he said.

Ukrainians have reacted with a mixture of concern and mockery to the narrative pushed by the Kremlin and Russian state media that Ukraine was behind the terrorist attack Friday on a Moscow concert hall, a claim made despite the Islamic State’s claim of responsibility.

For some Ukrainians — officials and citizens alike — the accusations were typical of a Kremlin playbook, blaming Ukraine to justify Moscow’s violence against their country. That includes the false claim that President Vladimir V. Putin of Russia used to begin the full-scale invasion of Ukraine, stating that the country was run by neo-Nazi leaders and that the aim of the war was to denazify the country.

“It’s typical for Russia,” Iryna Blakyta, 24, a resident of Kyiv, said on Monday, adding that she expected Mr. Putin to use the attack on the concert hall to rally Russians after more than two years of war. “He needs to mobilize people,” Ms. Blakyta said; “he needs to show who the enemy is.”

But worries about Mr. Putin’s next steps intensified on Monday morning in Kyiv, which was targeted by two ballistic missiles in broad daylight, the third air assault against the Ukrainian capital in five days. A university building in a central part of the city was reduced to rubble, and officials said at least 10 people had been injured.

The United States has confirmed the claim of responsibility by ISIS. And, on Monday night, Mr. Putin acknowledged that “radical Islamists” had executed the attack, but he also said Ukraine, backed by the West, could have masterminded the assault. Ukraine denied any involvement.

Ukrainian officials said Mr. Putin’s hints that Ukraine was involved were in line with the Kremlin’s longstanding practice of sowing disinformation to cover up the failings of its security services.

“Putin is a pathological liar,” Dmytro Kuleba, Ukraine’s foreign minister, wrote on X on Sunday, listing a series of bombings, murders and aggressive actions by Russia that he said were all cloaked in lies, including Russia’s illegal occupation of Crimea in 2014 and the downing of an airliner over Ukraine by Kremlin-backed fighters the same year.

“Do not let Putin and his henchmen dupe you,” Mr. Kuleba said.

Mr. Putin had earlier claimed in a statement about Friday’s attack, which killed at least 139 people, that the suspects “were heading toward Ukraine” after rampaging through the concert hall and that “according to preliminary information, a window was prepared for them on the Ukrainian side to cross the state border.” He stuck to this claim on Monday.

But Andriy Yusov, a representative of Ukraine’s military intelligence agency, ridiculed that claim over the weekend, saying that the Ukrainian-Russian border is an active combat zone that is heavily mined and guarded by both sides — making any crossing extremely complicated and dangerous.

“You don’t need to be a security expert” to understand this, Mr. Yusov said on Ukrainian television on Saturday.

He and other officials have pointed to Russia’s use of previous terror attacks to pursue political goals, including Mr. Putin using a deadly school siege in 2004 to consolidate political control over the country’s regions, abolishing direct governor elections until their restoration in 2012.

Some Ukrainian officials and analysts have said that Russia’s attempts to shift the blame to Ukraine could be used to lay the groundwork for expanding conscription. Russia has captured several cities and villages in Ukraine in recent months, but at considerable human cost, making it crucial to replenish its forces.

“Their only goal is to motivate more Russians to die in their senseless and criminal war against Ukraine,” Mr. Kuleba said.

Mykola Davidiuk, a Ukrainian political analyst, said Mr. Putin wanted to portray Ukraine as “a cruel enemy” linked to terrorism in order to stir up “aggressive attitudes toward Ukraine among Russian people.”

But he added that Ukrainians “don’t care” about this narrative because they have long been used to the Kremlin’s spurious portrayal of the conflict.

For now, people in Ukraine were left wondering whether Mr. Putin would use the terrorist attack to justify more deadly strikes against Ukraine. “He needs to constantly create some reasons, to keep things in control,” Ms. Blakyta said.

On Monday at around 10:30 a.m., residents of Kyiv were startled by a series of loud bangs that came less than a minute after air raid alerts blared across the capital, prompting people to run in the streets to get to shelter.

The Ukrainian Air Force said it had intercepted two ballistic missiles launched from Crimea, but falling debris destroyed a university gym. “Fortunately, there was nobody inside because it was closed,” Mayor Vitali Klitschko of Kyiv said as he visited the site of the strike.

Nearby, investigators were busy collecting and marking missile debris to analyze and determine exactly what kind of weapon was used. Because the missiles streaked into Kyiv quickly after the alarm sounded, there has been speculation that Russia used one of its powerful hypersonic missiles, which fly at several times the speed of sound.

All that remained of the university building that was hit was a huge pile of bricks, twisted metal structures and broken concrete slabs. Cars nearby were covered in a thick layer of dust, and local people watched as rescuers and firefighters cleared away the rubble, still in shock at what had happened.

“A column of smoke and dust rose, just like in a fog. Then, sirens, rescue vehicles, emergency services,” said Evelina Korzhova, 30, standing in her flower shop, which faced the destroyed building. The shop’s glass window had been shattered by the blast.

In his evening address on Sunday, President Volodymyr Zelensky of Ukraine said that over the past week Russia had launched some 190 missiles, 140 attack drones and 700 aerial bombs at Ukraine.

Oleksandra Mykolyshyn, Paul Sonne and Daria Mitiuk contributed reporting.