Police in Hong Kong have charged five men with conspiracy to commit arson over a small blast outside the parliament earlier this month.

The men, aged between 18 and 24, were charged on Wednesday and are to appear before a court later in the day, a police spokesman said, adding that a sixth man, aged 22, was freed on bail without charge and must report to police next month.

The accused, four of whom are college students, were detained on Monday in connection with the December 9 explosion in a garbage can outside the legislature. They put a gas canister in the trash can and detonated it after wrecking a fire alarm. No one was wounded in the blast.

The blast took place hours after a debate about a controversial copyright bill was postponed because not enough lawmakers had turned up.

Media reports said two of the six individuals in the parliament explosion case were members of a pro-independence group that had rallied online against the bill. Opponents believe the bill aims to restrict freedom of expression.