The grenade went off in Barangay Tambis in Barobo town, Lt Col. Daniel Lucero, spokesman of the Armed Forces’ Southern Command, said.
Lucero said five people were killed, but he did not give their identities. Fifteen others are being treated at a hospital in nearby Prosperidad town, he added.
The authorities are attempting to determine who was responsible, the spokesman said. Communist guerrillas are known to operate in the region.
"The police and the military in the area are looking into the identity of the perpetrator and his motive," Lucero said. — Roel Pareño, AFP