ZAMBOANGA CITY - At least three people were wounded in two separate explosions that rocked Basilan province in southern Philippines on Sunday, police said Monday.

Chief Inspector Ariel Huesca, Western Mindanao regional police spokesman, said a grenade blast injured three laborers who were stockpiling bags of sand in Malamawi island off Isabela City on Sunday morning.

Initial investigation conducted by police revealed that a fragmentation grenade without its safety pin, which was placed among the bags of sand, detonated after one of the workers removed a bag.

Huesca said an improvised bomb exploded outside the house of a village chief in this city also on Sunday.

The improvised explosive device, which contained nails, was rigged in the fence of the house owned by Hadji Attang Mohammad in Mampang village.

Police said no one had claimed responsibility for the attack.