12 churchgoers have been injured in a grenade explosion outside a Catholic church in the southern Philippines.

Police say the worshippers were attending Christmas Eve masses in the town of Midsayap late Saturday, when unidentified men lobbed a grenade.

The victims suffered minor injuries, except for one who was critically wounded. No group has claimed responsibility for the attack.

However, Muslim rebels and Islamist extremists are active in the southern Philippines. There have been blasts there in the past.