The Liaison Office of the Central People's Government in the Hong Kong Special Administrative Region backs the police arrest of four members of a local political group for refusing to surrender information in a national security investigation.

The office said in a statement on Wednesday it supports the police to continue to look into the Hong Kong Alliance in Support of Patriotic Democratic Movements of China and the people behind the group in accordance with the law.

The statement came after the Hong Kong Police's National Security Department on Wednesday morning arrested four members of the alliance on suspicion of acting as a "foreign agent".

The alliance refused to comply with the police's request for information on Tuesday, the deadline given.

The arrest of the four – who blatantly refused the request, was made under Schedule 5 of the Implementation Rules for Article 43 of the Hong Kong National Security Law (Implementation Rules).

The office said the arrest is fair and just, as there must be consequences for violation of the law.

In two separate statements, the Office for Safeguarding National Security of the Central People's Government of the People's Republic of China in the Hong Kong Special Administrative Region and the city's Security Bureau also weighed in by supporting the move.

A spokesperson for the Office for Safeguarding National Security stressed anyone who violates the National Security Law and other laws in the city must be dealt with in accordance with the law.

The office supported the police to perform their duty to effectively prevent and punish acts and activities endangering national security.

"Ignoring warnings given, the organization concerned resolutely insisted on refusing to comply with the police's requirement to provide information pursuant to Schedule 5 of the implementation rules. Hence, the police have to take action," a spokesman for the Security Bureau said.

The Security Bureau reiterated any action taken by law enforcement agencies is based on evidence, strictly follows the law, and is solely a response to the acts of the persons or entities concerned.

Schedule 5 of the Implementation Rules clearly stipulates the consequences of not complying with the relevant submission requirements, i.e. being liable for conviction on indictment to a fine of HK$100,000 and imprisonment for six months, the spokesperson added.