ZAMBOANGA CITY, (AA) – Around 15 people were injured overnight when a grenade was thrown during a festival in the Southern Philippines, according to police and military — the fifth bombing incident in Central Mindanao in just two weeks.

The explosion occurred in the provincial capital of Sultan Kudarat as it celebrated the province’s anniversary, according to the Notre Dame Broadcasting Corp.

Supt. Jemuel Siason, chief of Sultan Kudarat police public safety battalion, reported that an unidentified man lobbed a grenade at second-hand clothing and ornamental plants stalls in Isulan at around 8.30 p.m. (1230GMT) Saturday.

Siason said the blast occurred around 20 meters from a gas station and a few meters from a gymnasium where the festival was being celebrated.

Victims — including three schoolchildren — sustained shrapnel wounds and were rushed to the local hospital for treatment.

Senior Superintendent Danny Reyes, provincial police director, said investigators were still trying to establish the identities of the culprits and the motive behind the attack.

“Most of the wounded victims were 15 revelers including ‘ukay-ukay’ [second-hand clothing] patrons,” he said.

In the past fortnight, Isulan has suffered by four grenade attacks — three in Kabacan, North Cotabato (which left six people wounded), and another in Cotabato City.

Police security forces arrested a motorcycle rider for possession of a grenade early Sunday in North Cotabato — the same type of explosive used in recent attacks in North Cotabato.