Three former members of a Hong Kong group that organised annual vigils to mark China’s 1989 Tiananmen Square massacre, have been sentenced to four and a half months in jail for not complying with a request for information under a Beijing-imposed national security law.

Thirty eight year old Chow Hang-tung, a prominent Hong Kong pro-democracy activist and former vice chairperson of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, was sentenced at a magistrate’s court on Saturday alongside two co-defendants.

Announcing the custodial sentence that fell short of the six-month maximum jail term allowed for the charge, magistrate Peter Law said “national security is cardinally important to public interests and the whole nation”.

The now-disbanded alliance was the main organiser of Hong Kong’s June 4 candlelight vigil for victims of China’s Tiananmen Square, where in 1989 Chinese troops and tanks were deployed against peaceful pro-democracy protests.

Every year, the vigil had attracted tens of thousands of people in the largest public commemoration of its kind on Chinese soil.