One soldier was killed and another was injured after an explosion hit a military facility in south Philippine city of Cotabato on Thursday night, a military official reported Friday.

Jo-ann Petinglay, public affairs officer of the Army's 6th Infantry Division, said the explosion was believed to have been caused by an 40 mm round grenade, based on initial assessments.

Petinglay said the explosion occurred at around 7:30 p.m. beside the guard post of the 5th Special Forces Battalion headquarters along Notre Dame Avenue, Rosary Heights 2.

She said two soldiers were injured in the explosion, but one of them was declared dead while undergoing treatment at a hospital.

Authorities are still investigating the identities of the suspects and their motive.