Antony Blinken is a seasoned Obama-era foreign policy adviser and, once confirmed by the Senate, will succeed a staunch China critic in Mike Pompeo.

He tweeted in support of Hong Kong’s pro-democracy movement on Wednesday after local police confirmed they had arrested 53 activists for violating the city’s national security law.

The operation involved around 1,000 law enforcement officers who launched dawn raids at 72 locations, Hong Kong police told reporters.

“The Biden-Harris administration will stand with the people of Hong Kong and against Beijing’s crackdown on democracy,” Blinken wrote on Twitter.

Beijing sent a warning to the next American government later the same day, with foreign ministry spokesperson Hua Chunying voicing support for the authority of the Hong Kong police.

“Hong Kong enjoys law and order,” Hua told reporters at a regular briefing. “No other country has the right to make wanton criticism or interfere.”

The United States should “respect facts and the rule of law,” she added, while calling on Washington to “stop fabricating all sorts of pretexts for wanton political suppression and restrictions against China.”

Authorities in Hong Kong said Wednesday’s arrests were in connection with an unofficial primary election held in July 2020.

The event was organized by pro-democracy lawmakers, academics and students in order to thin the field for last September’s Hong Kong legislative election—which was later postponed by a year, purportedly over public health concerns.

Among those arrested under suspicion of “subverting the state”—a crime that carries a maximum sentence of life imprisonment—was Hong Kong human rights lawyer and U.S. citizen John Clancey, with the firm Ho Tse Wai and Partners.

Clancey is believed to be the first foreign national arrested under the sweeping national security law introduced by Beijing last June. He was released without charge on Thursday, while others were remanded on bail and are expected to report to police stations at regular intervals.

In a press statement on the State Department’s website, Pompeo called the mass arrests an “outrage.”

He said the U.S. government would consider sanctions against officials involved in the arrests and may target Hong Kong’s trade offices in America.

On Thursday, the Office of the United Nations High Commissioner for Human Rights joined world leaders and other rights groups in expressing “deep concerns” about the arrests.

“These latest arrests indicate that—as had been feared—the offence of subversion under the national security law is indeed being used to detain individuals for exercising legitimate rights to participate in political and public life,” said OHCHR spokesperson Liz Throssell.

“OHCHR and independent U.N. human rights experts have repeatedly warned that offences such as subversion under the national security law are vague and overly broad, facilitating abusive or arbitrary implementation,” the statement said.