The 39-year-old detainee, Max Chung Kin-ping, has been accused of calling for an unauthorised assembly, the HKRT broadcaster reported.
Meanwhile, the police fired tear gas at demonstrators during an authorized protest on Sunday. The rally began at 15:00 local time (07:00 GMT). Later in the day, some protesters went off the prescribed route, blocking central streets. At 18:05 local time, the police warned the demonstrators that tear gas could be fired. An hour later the police raised a red flag, which signals that the police will use force to disperse the crowd.
On Saturday over 288,000 people took to the streets in Yuen Long, a town in the northern New Territories of Hong Kong, despite a police ban on the protests. The crowds were protesting against the now-suspended bill that would allow extraditions to mainland China, and attacks targeting the protesters by triad members and local villagers.
Mass rallies erupted in Hong Kong in early June as the authorities were considering adopting a bill that would allow the autonomous Chinese city to extradite suspects to jurisdictions with which it did not have an extradition agreement, including mainland China. Pressured by the protests, the government indefinitely suspended the bill, while Hong Kong Chief Executive Carrie Lam issued a public apology. However, the protesters still demand the complete withdrawal of the extradition amendments.