HONG KONG (AP) — Hong Kong's highest court on Thursday revoked media tycoon Jimmy Lai's bail after prosecutors succeeded in asking the judges to send him back to detention.

Lai had been granted bail on Dec. 23 after three weeks in custody on charges of fraud and endangering national security. His appeal hearing is slated for Feb. 1.

The court said Thursday that it was “reasonably arguable" that the previous judge's decision was erroneous and that the order of granting bail was invalid.

Lai is among a string of pro-democracy activists and supporters arrested by Hong Kong police in recent months as authorities step up their crackdown on dissent in the semi-autonomous Chinese territory.

He was charged with fraud on Dec. 3 for allegedly violating the lease terms for office space for the Next Digital, the media company he founded. He was later charged again on Dec. 12 under the sweeping national security law imposed by Beijing on suspicion of colluding with foreign forces and endangering national security.

Lai entered the Court of Final Appeal without making any comments to supporters and media, many of whom swarmed the tycoon as he made his way into the courtroom. His bail conditions included surrendering his travel documents and a ban on meeting with foreign officials, publishing articles on any media, posting on social media and giving interviews.

Chinese state-owned newspaper People’s Daily posted a strongly worded commentary on Sunday criticizing the court for granting bail to Lai, stating that it “severely hurt Hong Kong’s rule of law.”

The People’s Daily said that it would not be difficult for Lai to abscond, and called him “notorious and extremely dangerous.” It also warned that China could take over the case, according to Article 55 of the national security law which states that China can “exercise jurisdiction over a case concerning offence endangering national security.”

Hong Kong’s judiciary on Tuesday uploaded a 19-page judgment on its website, laying out the reasons why High Court Judge Justice Alex Lee had granted Lai bail. Lee said that he was satisfied that there was no flight risk in Lai’s case, and noted that Lai was willing to have his movements monitored if it had been a feasible option.

On Tuesday, Lai resigned as chairman and executive director of Next Digital, which runs the Apple Daily newspaper, according to a filing made to the Hong Kong stock exchange. He did so “to spend more time dealing with this personal affairs” and confirmed that he had no disagreement with the board of directors, the filing said.