Several prominent critics of the Chinese government, including protest leaders in Hong Kong and pro-democracy activists in the United States, have accused Zoom of shutting their accounts and severing live events in recent weeks under pressure from Beijing.

The three incidents are reviving concerns about the fast-growing Silicon Valley company’s susceptibility to Chinese government influence weeks after the firm began facing scrutiny over security, including its routing of data through China. Coming in the midst of the coronavirus pandemic, the episode also highlights the world’s dependency on services such as Zoom and their ability to control speech.

Zoom on Thursday acknowledged that “a few recent meetings” related to China have been disrupted. The company said it was notified by Chinese officials beginning in late May about four upcoming “illegal” political events that they demanded be terminated. Zoom cut short two of the meetings while they were in progress after determining from IP addresses that users from China were participating, the company said, adding that it did not hand over any user or meeting information to the authorities.

In each instance, event organizers told The Washington Post that they relied on Zoom in lieu of in-person events because of social distancing and travel restrictions. And each of the Zoom accounts and events was created and hosted outside mainland China but appeared to be quashed under Chinese government pressure after they were publicly advertised.

Lee Cheuk-yan, a union leader and Labour Party figure in Hong Kong, said a Zoom account he used to host talks was shut down without explanation on May 22 just 30 minutes before he was scheduled to stream a talk by Jimmy Sham, a leading Hong Kong pro-democracy activist.

The talk, which had been promoted in Hong Kong protest circles, went ahead and was streamed on YouTube and Facebook without incident, Lee said, but his Zoom account remains disabled.

In the first week of June, Zoom also shut down a private account of Zhou Fengsuo, a California-based Chinese dissident, days after he hosted a videoconference commemorating Beijing’s bloody crackdown in Tiananmen Square on June 4, 1989, according to Zhou.

And on June 3, a separate Tiananmen commemoration was severed after the Zoom account that hosted it was deactivated midstream. The live event that began with 200 participants suffered two disruptions that “practically destroyed it,” said one of the organizers, former Tiananmen student protest leader Wang Dan, who is based in Washington.

In statement, Zoom said it was obliged to respond to requests from Chinese authorities as long as users in China participated in videoconferences.

“Like any global company, Zoom must comply with laws in the countries where we operate,” a company spokesman said.

“We regret that a few recent meetings with participants both inside and outside of China were negatively impacted and important conversations were disrupted. It is not in Zoom’s power to change the laws of governments opposed to free speech. However, Zoom is committed to modifying its processes to further protect its users from those who wish to stifle their communications.”

All three accounts have been restored, the company said.

Chinese Foreign Ministry spokeswoman Hua Chunying said at a regular press briefing Thursday that she was not aware of attempts to shut down Zoom meetings.

Lee, the Hong Kong union chief who is also known for organizing an annual commemoration of the Tiananmen Square crackdown on June 4, said he wanted to host his talk series on Zoom, as well as YouTube and Facebook, precisely because Zoom remains accessible within China, unlike the latter two services, which are censored.

“We used Zoom because we wanted to reach as many people as possible inside China,” Lee said. He speculated that Zoom caved to Chinese pressure because it did not want to be banned in the country like YouTube and Facebook.

Lee said he was concerned that Zoom was censoring a virtual talk in Hong Kong at the behest of the Beijing government, which is obligated to grant the city a degree of political autonomy and civil freedoms under a 1984 agreement between China and Britain.

“Zoom already destroyed one-country, two-systems before even they did,” Lee said, referring to the Chinese government’s push to enact a national security law in Hong Kong that critics say would eliminate the city’s autonomous status.

The two other Zoom accounts that were shut down were tied to the most sensitive event in China’s modern history: the killing by the military of hundreds of pro-democracy protesters around the country before dawn on June 4, 1989.

Although domestic security agencies and censors routinely snuff out discussion and commemoration of the incident, which posed an existential threat to the Communist Party and deeply tarnished its image, there is no Chinese law that explicitly bans vigils and commemorations of an event that has effectively been erased from official public discourse.

Zhou, the California-based activist, said Zoom restored his account Wednesday after an inquiry from Axios, which first reported the closures of Zhou’s accounts. Zhou’s account had been disabled after he hosted a May 31 public videoconference with about 250 participants and speakers that included a group of Chinese mothers whose sons were killed by troops in 1989.

Chen Yunfei, a Chinese dissident in the city of Chengdu, delivered a video address at that event. A day later, he was detained by police and locked in a hotel room for five days, a common form of punishment known as “soft detention.”

“Zoom is acquiescing to an oppressive and inhumane government,” Chen said by telephone this week upon his release. “I wish they would consider that before their material profits.”

Zoom videoconferencing has become an essential part of global business, government and everyday life since the coronavirus outbreak. Its share price has more than tripled this year, with the company announcing daily users have jumped from 10 million in December, before the pandemic, to 300 million in April.

But the company has come under scrutiny for its security practices and acknowledged in April that it routed non-China calls through servers in China. In response to a report by the Toronto-based Citizen Lab cyber-research group, Zoom said it would begin “geo-fencing” to ensure data traffic between two customers outside China would no longer pass through Chinese servers.

Still, some companies and government agencies in the United States, Taiwan, Australia, Germany and Britain have warned their staffs against using the service.

Chief Executive Eric Yuan pledged in April that he would not develop new features on Zoom before he patched up videoconference security.

But for global technology companies, demands from government censors pose a more complex and delicate problem, given their need to operate across a country-by-country patchwork of political terrain and restrictions.

Technology companies frequently turn over private information requested by government agencies, including those in the United States, and businesses other than Zoom routinely submit to Chinese government censorship demands.

The mainland China version of Microsoft’s Bing search engine, for instance, returns no relevant results for the Tiananmen incident. In 2004, Yahoo handed to authorities the email records of a Chinese journalist, Shi Tao, who leaked a censorship directive about that year’s Tiananmen anniversary. Shi was subsequently sentenced to 10 years’ imprisonment.

Wang, one of the student leaders in 1989 and for a period the most wanted fugitive in China, criticized Zoom’s explanation that it needed to obey “local laws.”

“What about American values? It’s an American company,” Wang said. “They should maintain a moral bottom line.”