Hong Kong police raided the private offices of pro-democracy media tycoon Jimmy Lai on Thursday, according to Lai and his aide, Mark Simon.

More than a dozen officers carried out the raid and it was unclear what they were looking for, Simon said on Twitter, adding that the police did not leave behind identification or contact information.

"I spoke with police they said they would remain until our lawyer arrived,'' Simon tweeted. "They did not, they took documents and departed before our lawyer arrived.''

Lai is the founder of the publishing company Next Digital, which runs Hong Kong's pro-democracy newspaper Apple Daily. He is an outspoken figure in Hong Kong's pro-democracy movement and regularly criticizes the Hong Kong government and Beijing's authoritarian rule.  

Lai in court on 'unlawful assembly' charges 

The raid comes ahead of Lai's scheduled court appearance Thursday, where he will face charges of "joining an unauthorized assembly" leveled against him for taking part in a candlelight vigil marking the anniversary of the Tiananmen Square massacre on June 4.

Read more: Jimmy Lai: ‘National security law is Beijing’s death knell for Hong Kong’

"They just wanted to get something to go against me," Lai told reporters before entering the court. "That's not rule of law," Lai said. "They just took everything."

Several other pro-democracy activists including Joshua Wong, Lee Cheuk-yan and Leung Kwok-hung are also due to appear in court.

The vigil was retroactively considered illegal under Hong Kong's new national security law, which came into force June 30, and outlaws "subversion, secession, terrorism, and collusion."

Read more: China's security law: The end of Hong Kong's semi-autonomous status?

Lai: 'I am not going away' 

The law has drawn international condemnation as a tool for Beijing to curb free speech, freedom of assembly and rule of law in semi-autonomous Hong Kong.

Lai was arrested in August on "suspicion of colluding with foreign forces," and the headquarters of Next Digital were raided and its funding frozen. He was released on bail.

Read more: Opinion: China to rule Hong Kong by fear with new national security law

"I'm not worried and I'm not going away. I will stay in Hong Kong and fight until the last day. It doesn’t matter whether I'm one of the prime targets or not," Lai told DW on June 29.

wmr/rc (AP, Reuters)