A Hong Kong internet radio host was arrested on Sunday under a little-used colonial era sedition law that authorities have begun to wield against Beijing's critics.
Officers from the police's national security department arrested 52-year-old Wan Yiu-sing on a charge of "seditious intent", according to a police statement.
Authorities did not disclose what Wan had said or did that was potentially seditious.
The radio personality, better known by his DJ name "Giggs", has hosted programmes discussing anti-government demonstrations and previously called for donations to support young Hong Kongers who have fled to nearby Taiwan.
Hong Kong's sedition law is separate to a sweeping national security law that Beijing imposed on the city last summer in a bid to stamp out dissent.
Instead it dates back to the mid-19th century during British colonial rule.
It remained on the books after the 1997 handover to China but was never used in a city that has enjoyed political freedoms unseen on the Chinese mainland.
But after 2019's huge and often violent democracy protests, prosecutors dusted off the law.
Last September another pro-democracy radio host, Tam Tak-chi, became the first person to be charged with sedition since the handover.
He is currently in custody awaiting trial.
Prosecutors allege that popular protest slogans he uttered, such as "Liberate Hong Kong, revolution of our times" and "Disband the police", were seditious.
Sedition is classified as words that incite "hatred or contempt" for the government or cause discontent and dissatisfaction among residents.
Tam's coming trial will be a legal test case for how sedition sits with the freedoms of speech supposedly guaranteed by Hong Kong's mini-constitution and its bill of rights.
Beijing's national security law has peeled back on those liberties.
It has quashed protests and effectively outlawed a host of peaceful political views, including advocating for independence, greater autonomy or full democracy in Hong Kong.
Wan was previously arrested on a national security charge last year, one of more than 100 dissidents investigated under the new powers since they came into force in June.
At the time the police's national security department said they suspected Wan had illegally processed funds to support people or organisations that advocate secessionist activities -- a potential reference to donations for Hong Kongers in Taiwan.
He has yet to be charged with a national security offence, and his arrest on sedition may indicate police have decided to use the colonial era law instead.