HONG KONG, Aug. 30 (Xinhua) -- Three leaders of political groups advocating "Hong Kong's independence," Joshua Wong Chi-fung, Agnes Chow Ting and Andy Chan Ho-tin, have been detained, Hong Kong police confirmed Friday.

Wong was arrested at around 7:30 a.m. Friday enroute to the South Horizons MTR station, according to the social network account of his group Demosisto.

It said that Wong was arrested on three charges and was taken to the police headquarters in Wan Chai.

Following Wong's arrest, Chow was detained at her home, it said.

Chan said on his social network account that he was detained Thursday night at Hong Kong International Airport as he was preparing for departure.

Chan was the leader of Hong Kong National Party, a political group that has been announced illegal by the Hong Kong Special Administrative Region (HKSAR) government.

The Hong Kong police confirmed with Xinhua that its Organized Crime and Triad Bureau (OCTB) launched an operation on Friday morning and arrested a 22-year-old male surnamed Wong and a 22-year-old female surnamed Chow in connection with the besiege of the police headquarters on June 21.

Wong was arrested on charges of "inciting others to participate in unauthorized gatherings," "organizing unauthorized gatherings" and "knowingly participating in unauthorized gatherings."

Chow was arrested on charges of "inciting others to participate in unauthorized gatherings" and "knowingly participating in unauthorized gatherings."

The OCTB arrested a 29-year-old male surnamed Chan at the airport on Thursday night, the police said, adding that the man was detained for enquiries in connection with riots and assaults on police personnel during a demonstration in Sheung Shui on July 13.

A person who is convicted with rioting faces up to 10-year imprisonment, said Grenville Cross, honorary professor of law with the University of Hong Kong and former director of public prosecutions, on Friday.

Last year, the Hong Kong Court of Final Appeal made clear that cases of public disorder that involve violence would be severely dealt with.

"I would expect the courts to keep in mind what the court of final appeal has said and to pass serious sentences," he said.