Hong Kong (CNN)Four activists from the Hong Kong pro-democracy group that organizes the city's annual Tiananmen Square vigil were arrested early Wednesday morning, after the group refused to comply with a police order to submit information on national security grounds.
National security police arrest organizers of Hong Kong's Tiananmen vigil
Police had sought details concerning the group's funding and membership in relation to an accusation it was working as a "foreign agent," in violation of the city's sweeping national security law, according to a letter seen by CNN late last month.
The letter said the group, the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, had 14 days to submit the information, or face up to six months' imprisonment.
Under the law, which was imposed by Beijing last year, authorities have wide-ranging powers to crack down on political crimes.
The arrested members of group included vice chairwoman and barrister Chow Hang-tung, as well as standing committee members Leung Kam-wai, Tang Ngok-kwan and Chan Dor-wai, the group said.
Chow posted on social media early Wednesday morning that police were ringing her doorbell and attempting to open the door.
In a statement Wednesday morning, police confirmed they had arrested four individuals under the national security law, though neither the statement nor the police press office would identify their names or that they were members of the Hong Kong Alliance.
The four individuals are accused of failing to comply with the implementation of the national security law, said police.
"Police operations are continuing, and it cannot be ruled out that more people may be arrested," the statement added.
The Alliance, formed more than three decades ago to support those protesting for democracy in Beijing, said on Sunday that it would not comply with the police request, which included orders to hand over its members' personal details, as well as all meeting records with political groups in Hong Kong, Taiwan and overseas.
The city's security agency released a statement later Sunday with a "solemn warning" that "endangering national security is a very serious crime," and that the Alliance "should immediately turn back before it is too late."
But the group doubled down on Tuesday, submitting a letter to police arguing they had insufficient grounds to request materials. In their letter, the group added that it was not a "foreign agent," and that police had yet to explain why they believed the group was linked to foreign forces.
Tsui Hon-kwong, a member of the alliance, said on Tuesday that a judicial review had been filed to challenge the police request.
In response, Carrie Lam, the city's leader, criticized the group for disobeying police. "I must strongly condemn (the Alliance's) statements," Lam said on Tuesday. Security Chief Chris Tang also warned on Tuesday that those who do not comply with national security police orders would face consequences.
Hours later, in the early hours of Wednesday morning, the arrests were carried out.
The Hong Kong Alliance has held an annual candlelight vigil on the anniversary of the Tiananmen pro-democracy crackdown since 1990.
The events of Tiananmen Square began with protesters in Beijing, mostly college students, gathering in the heart of the Chinese capital to mourn the death of an ousted former leader -- then, to push for governmental reform and greater democracy.