Five more people have been arrested in connection with an attack on a corrections officer outside Pik Uk Prison last week.

That brings to 13 the number of people arrested over the case.

Police said of the latest arrests, three were suspected to have carried out or planned the attack and two others allegedly provided assistance to the assailants.

At least one of them has been charged.

Eight others were taken into custody earlier and three of them have been charged.

Officers have not ruled out making further arrests.

According to the police, the officer was attacked by three masked men carrying "long hard objects" while waiting for a bus outside the prison in Sai Kung on Friday.