The first blast caused panic among local residents, prompting the police to tighten security in all of the 37 barangays here.
Investigators said a lone suspect tossed a Mark II fragmentation grenade inside the yard of Hadji Osmeña Montañer, Budget Officer of DAs Central Mindanao regional office, and escaped using a motorcycle.
No one was killed or wounded in the blast, but two cars parked on the spot where the grenade fell were riddled with shrapnel.
Policemen investigating the grenade attack in Montañers residence said they are looking into possibility that the bombing could be related to his work, or to a standing "rido," or family feud with an equally influential clan in his hometown in Malabang, Lanao del Sur.
The incident was followed by another grenade explosion at a hillside slum area here.
Police and Army bomb experts said somebody from the national highway overlooking the residential area, a known lair of drug peddlers, hurled a fragmentation grenade atop the roof of one of the houses there and fled.
Preceding the two grenade blasts was the prompt detonation by Army ordnance experts of an M-67, apple-type grenade found at the front yard here of Jose Acosta.
The grenades pin and safety lever was rigged with a trip wire attached to the gate of Acostas yard.