Senior Supt. Benhur Mongao, Sultan Kudarat police director, said they received reports that the grenade attacks were allegedly test missions carried out by new recruits of local terrorist cells, which he did not name.
"They may have switched to grenade attacks instead of planting explosives because of the tight security," he said in a radio interview.
Mongao said Sultan Kudarat investigators are currently comparing notes with their counterparts in General Santos City to determine a possible pattern in the grenade attacks.
The latest attack occurred at a carnival in front of the City Hall building of Tacurong City in Sultan Kudarat on Saturday night and injured seven persons.
He said four of the victims are still confined at a private hospital in Tacurong City.
On New Year's Eve, at least 26 persons were injured when a grenade exploded at a crowded portion of the oval plaza in General Santos City.
Prior to the attack, a grenade explosion also ripped through a local police station that injured two policemen.
Mongao said they could not yet pinpoint any suspect but he confirmed that they are already following several leads that may point to those possibly behind the Saturday night grenade attack.
He said they included in their investigation the possible involvement of a suspected bomber who was arrested in Lambayong town last week.
"We're following up some angles and we're hoping they would yield positive developments in the coming days," he said.
In the meantime, Mongao said the provincial police office issued a recommendation to the local government of Tacurong to put on hold the operations of the carnival to prevent another possible attack.
He also urged Sultan Kudarat residents to remain vigilant against possible attacks by local terror groups.
On New Year's Eve, authorities detonated a powerful bomb planted inside a passenger bus parked at the public terminal of Isulan town.
The explosive was found a day after a 17-year-old tricycle driver was killed in a bomb explosion in Esperanza town. (Allen V. Estabillo/MindaNews)