Zoom suspended the U.S.-based accounts of activists marking the anniversary of China’s Tiananmen Square crackdown on its platform, drawing criticism that the firm whose product has quickly become ubiquitous in quarantine life is not committed to protecting free speech.

On May 31, the U.S.-based human rights campaign group Humanitarian China used Zoom to connect a group of more than 250 people to commemorate June 4, 1989 — the day Beijing violently crushed peaceful pro-democracy protests in the heart of the capital, killing anywhere from several hundred to thousands of participants. Numerous people dialed in to the virtual event from within China.

A week later, on June 7, the host’s paid Zoom account was shut down without explanation. It was reactivated again on Wednesday.

Another memorial that the US-based Chinese activists sought to hold via Zoom on June 4 itself was twice cancelled, with two of their paid accounts disabled, according to the Financial Times. They remain inactive as of Thursday.

Nasdaq-listed Zoom has admitted it shut down the accounts, saying it was complying with “local laws.” In a statement, it explained, “Just like any global company, we must comply with applicable laws in the jurisdictions where we operate.”

But China has no laws against commemorating Tiananmen or criticizing the ruling Communist Party, although authorities has punished people doing so by charging them with other crimes.

Humanitarian China shot back in a statement that “if so, Zoom is complicit in erasing the memories of the Tiananmen Massacre in collaboration with an authoritarian government.”

The period around June 4 is one of the most politically sensitive times of the year for China, whose repressive censorship regime kicks into even higher gear around the anniversary. The highly monitored Chinese internet is scrubbed of all references to the event itself.

Zoom is not currently blocked by China’s “Great Firewall” of censorship, meaning it is accessible in the mainland without a VPN. The company has strong ties to China, home to nearly a third of its staff. It conducts much of its R&D and houses servers in the country. 

Last month, Zoom stopped allowing individual users in China to sign up for its services. And as of May 1, China-based users can join other meetings but will no longer be able to host them, according to the Nikkei Asian Review.

Prominent Tiananmen dissident Zhou Fengsuo, the co-founder Humanitarian China who hosted the May 31 Zoom meeting, told the South China Morning Post that their virtual event was the first time so many high-profile people with direct ties to the 1989 movement had been able to gather together. The group included the mother of a slain protester, multiple exiled student leaders like Zhou and a protester jailed for 17 years for his participation, among others.

“I’m very angry, of course, that even in this country, in the United States … we have to be prepared for this kind of censorship,” he told the paper.

Zhou’s activism has led him to other run-ins with Western internet firms toeing the Chinese Communist Party line. Last year, LinkedIn chose to hide his page from mainland users, saying the company had to comply with Chinese government requirements. After public outcry, it later reinstated the page.

Zoom’s shutdowns of accounts based out of China but affiliated with content that would rile Beijing extends beyond the U.S.

The Zoom account of Lee Cheuk-yan, a Hong Kong union leader involved in organizing the city’s annual Tiananmen memorial, was shuttered without explanation in late May, just a half hour before it was scheduled to stream a talk with Jimmy Sham, a prominent local pro-democracy activist, the Washington Post reported Thursday. It has yet to be reinstated.

Lee told the paper he suspected that Zoom was censoring the virtual talk in Hong Kong at the bidding of Beijing authorities, who should technically be allowing the “special administrative region” broader civil liberties and political freedoms than the mainland under the “one country, two systems” agreement.

PEN America, a nonprofit focused on defending free speech, said in a statement that Zoom should take action to reassure users that it stands against government-imposed censorship.

“We wouldn’t tolerate it if a phone company cut off service for someone expressing their views in a conference call; we shouldn’t tolerate it in the digital space either,” its CEO Suzanne Nossel said.

Zoom may seek to be the platform of choice for companies, schools and organizations during the pandemic, but “it can’t serve that role and act as the long arm of the Chinese government. You don’t get to have it both ways,” she added.