Several dozen Hong Kong democrats are due to report to local police stations across the city on Sunday, with some expecting to be charged with breaches of national security as a crackdown on the democratic opposition intensifies.

Benny Tai, one of the organisers of an unofficial primary election last summer, said in an online post that there was a chance he would be “formally charged”.

Tai was arrested in a dawn raid along with more than 50 other democrats on Jan 6 in the largest national security operation since the law’s passage last June.

They were accused of organising and participating in an unofficial “primary election” last July aimed at selecting the strongest candidates for a legislative council election.