An explosion at a local festival in the southern Philippines killed two people and injured more than 50 in a hail of shrapnel and an ensuing stampede Wednesday night, police said.

The blast occurred around 9:45 p.m. while people were dancing on a basketball court that had been turned into a trade fair during Labor Day celebrations at Notre Dame village, part of Catabatu city, police chief Sanggacala Dampac said.

Col. Edcel Soriano, the local military commander, said it appeared someone lobbed the grenade and ran. The safety pin was recovered.

The scene at the overwhelmed local hospital was chaotic. Nurses called for relatives of victims to donate blood for surgery.

The Philippines has been on a bomb alert since a trio of blasts 10 days ago in General Santos, also in the south, killed 15 people. Two suspects who were arrested the next day claimed there was a plan for more bombings to destabilize the country.

Police earlier Wednesday said they had stymied planned terrorist attacks in Davao city in the south and Tarlac in the north with pre-dawn clashes with men carrying bombs and grenades.