Maj. Gen. Generoso Senga, commander of the Armys 6th Infantry Division, said around 70 MILF guerrillas ambushed a group of Citizens Armed Forces Geographical Unit (Cafgu) militiamen accompanying several farmers harvesting their crops near Upi town in Maguindanao, killing seven of them and wounding two.
The rebels also fired rocket-propelled grenades at two Marine detachments in the town, but there were no immediate reports of casualties or injuries.
The military immediately retaliated by launching air assaults against MILF positions in the area, leaving 12 of them dead, Senga said.
Four MILF rebels were also killed and six others captured as troopers from the Armys 47th Infantry Battalion launched a preemptive raid against the guerrillas in nearby Datu Paglas town, also in Maguindanao.
Senga said the military strike was ordered after the rebels were seen massing nearby, possibly to sabotage a power pylon owned by the state-run National Power Corp.
The military said a 15-man MILF band led by Roco Baluda, alias Commander Roco, was also planning to attack the military detachment in Sitio Mayo, Barangay Columbio that prompted the government troops to conduct a preemptive strike.
"This is a treacherous act of the MILF to declare a ceasefire on one hand and attacking government troops on the other," Senga said.
The names of the slain rebels were not immediately known while those captured were undergoing tactical interrogation.
MILF spokesmen were not immediately available for comment.
Senga said the attacks confirmed suspicions that MILF leaders do not have complete control over their guerrillas.
President Arroyo on Friday rejected a 10-day truce offered by the MILF, dismissing it as a "tactical ploy" to buy time amid a massive anti-terrorist campaign in Mindanao.
"We will not stand for double talk. It is clear at this time, that the declaration of a ceasefire by the MILF is a ploy and a tactical ruse. Unless proof of sincerity is shown, punitive actions will continue," Mrs. Arroyo said.
The 12,500-strong MILF last Wednesday declared a unilateral ceasefire to begin tomorrow in support of efforts to bring a negotiated settlement to its 25-year campaign to set up a separate Islamic state in Mindanao.
But the separatist guerrillas demanded the government withdraw troops from rebel areas and recall arrest warrants for MILF chairman Hashim Salamat and their other leaders or face renewed fighting.
Mrs. Arroyo had earlier welcomed the peace overtures, but asked the rebels to categorically renounce links to terror groups such as the Indonesian-based Jemaah Islamiyah and Saudi dissident Osama bin Ladens al-Qaeda network.
She also demanded the rebels to surrender "the terrorists among them" responsible for a spate of bombings and raids in Mindanao that have left about 100 people dead since March.
But a day after the rebels announced the truce, MILF guerrillas raided three southern villages, burning houses in Carmen, North Cotabato, leaving six civilians and five of their comrades dead.
Following the declaration of the MILFs 10-day unilateral ceasefire, Southern Command chief Lt. Gen. Roy Kyamko said the troops are on the alert citing previous ceasefires that the separatist rebels took advantage of to regroup and stage attacks.
Soldiers have also intensified their confidence-building maneuvers with the local Muslim villagers to hasten the return of evacuees to far-flung areas and for them to deny sanctuary to MILF rebels.
The military said the low-level diplomatic initiative is also aimed at encouraging local residents to help monitor movements of MILF forces, in anticipation of further attacks.
Last Wednesday, Marines guarding the Buliok complex, the former MILF bastion in thattown, provided free medical and dental services to 1,780 relatives of active rebels in their first ever humanitarian project aimed at defusing tension in the area.
Meanwhile, police authorities in Lanao del Norte said they cannot effect the arrest of the MILF leaders and fighters who attacked Maigo and Kolambugan towns in that province last April 24.
Police provincial commander Senior Superintendent Laut Sarip claimed they have yet to secure a copy of the arrest warrant.
"I dont have in my possession the warrant of arrest," Sarip explained as he was asked why a certain Elias Api, an alleged MILF sub-commander of Abdulrahman Macapaar alias commander Bravo, was not arrested and brought to court.
Api was among the MILF rebels recently surrendered to government authorities last week.
The military has launched pursuit operations against three MILF commanders identified as Yahyah Lucsadato, Macapaar and one Commander Minsupala who led the attack in Maigo and Kolambugan towns. With Roel Pareño, Lino de la Cruz, Butch Enerio, Bong Fabe, AFP