Hong Kong police arrested a 24-year-old man at the city’s airport early on Thursday on suspicion of stabbing an officer during protests against a new national security law imposed by Beijing on the financial hub.

The arrest followed the latest protests on Wednesday in which police fired water cannon and tear gas and arrested more than 300 people as demonstrators defied the sweeping security legislation introduced by China to snuff out dissent.

There were no signs of protests on Thursday.

Police posted pictures on Twitter from Wednesday’s disturbances showing on officer with a bleeding arm saying he was stabbed by “rioters holding sharp objects”. The suspects fled while bystanders offered no help, the police said.

A police spokesman said the arrested man was surnamed Wong but could not confirm whether he was leaving Hong Kong or working at the airport.

Media, citing unidentified sources, said the suspect was on board a Cathay Pacific flight to London due to depart just before midnight. A witness said three police vehicles drove towards a gate as a Cathay Pacific plane was preparing to take off and about 10 riot police ran up the bridge to the aircraft.

The suspect held an expired British National Overseas passport, a special status which provides a route to citizenship, the source told the Cable TV station. Cathay Pacific did not respond to a request for comment.

Former Hong Kong leader Leung Chun-ying posted on Facebook on Wednesday that a bounty of $64,513 would be offered to anyone helping catch the fugitive.

China’s parliament adopted the security law in response to protests last year triggered by fears that Beijing was stifling the city’s freedoms and threatening its judicial independence, guaranteed by a “one country, two systems” formula agreed when it returned to Chinese rule in 1997. Beijing denies the accusation.