Hong Kong’s national security police arrested six people across the city on Tuesday under a new national security law known as Article 23 for alleged seditious intent, according to a statement.

Hong Kong’s security secretary, Chris Tang, told reporters one of those arrested was Chow Hang-tung, a prominent barrister and pro-democracy activist who is in jail on other charges.

Tang told reporters it was alleged that the group of people had used a Facebook page to “advocate hatred” against the Chinese and Hong Kong governments, as well as the judiciary.

Chow is alleged to have used the five others to “publish posts with seditious intent” focused on an “upcoming sensitive date”, the statement added. The offence carries a maximum jail term of seven years.

Local media cited sources as saying the date was June 4, the anniversary of a bloody crackdown on Chinese pro-democracy protesters in and around Beijing’s Tiananmen Square in 1989.

Those arrested were between 37 and 65, but Tang did not name the other five.

Chow was formerly one of the leaders of the Alliance — a pro-democracy group that used to organise an annual candlelight vigil to commemorate June 4 in a downtown park in Hong Kong, a British colony that reverted to Chinese rule in 1997.

The alliance was forced to disband under a security crackdown, and the vigils were banned. “Those intending to endanger national security should not delude themselves into thinking they can avoid police pursuit by remaining anonymous online,” the statement added.

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