Philippine police say two men on a motorcycle fired a grenade at the main gate of a Protestant church in the south, injuring at least four churchgoers.

Police said it was not immediately clear if Muslim rebels were involved in the attack late Wednesday at the United Church of Christ in the Philippines church in Pikit town in North Cotabato province. The attackers escaped.

Police said two victims are in critical condition.

Government forces have been on alert for possible attacks by a breakaway group of hard-line rebels opposed to a recently signed peace deal between the government and the Moro Islamic Liberation Front, the largest Muslim insurgent group.

The peace pact aims to establish a more powerful autonomous region for Muslims in the south of the largely Catholic nation.