Police on Thursday confirmed officers from the national security department had arrested 11 people for allegedly helping 12 Hongkongers flee the city by speedboat in August.

In a brief statement, a police spokesman said the eight men and three women, aged between 18 and 72, were being detained on suspicion of assisting offenders, but gave no further details.

Democratic Party district councillor and lawyer, Daniel Wong, wrote on social media that police turned up at his home at around 6am to arrest him.

Pro-democracy campaigner, Willis Ho, wrote on her Facebook page that her mother had been taken away.

The 12 Hongkongers were intercepted by Guangdong coast guard on the speedboat believed to be heading to Taiwan and detained for months, before 10 of them were found guilty and jailed for up to three years in a Shenzhen court. The remaining two, who were minors, were sent back to Hong Kong.

Police also arrested nine people in October on suspicion of helping the 12 escape. They were accused of providing them with the ship as well as accommodation, transport and money.

Last week, national security police arrested more than 50 pan-democrats for their alleged involvement in primary votes for Legco elections last year. Most of them were freed on bail without charge.