The Moro Islamic Liberation Front (MILF) also attacked with mortars two Army detachments near the Agus 4 hydroelectric plant operated by state-run National Power Corp. in the town of Matampay in Lanao del Norte, the military said.
There were no reports of injuries, but officials said the spillway of the power plant was partially damaged. Electricity supply, however, was not cut off or disrupted.
Local Army spokesman Capt. Alexis Bravo said the mortars were fired from about four kilometers away from the power plant, which was near the military detachment.
The Army retaliated by firing several rounds of mortar fire, which pushed back the MILF to hinterland areas, he said.
Additional troops were sent to the area to secure the plant which, if damaged, could trip power lines in major areas of Mindanao.
The MILF is the country’s main Moro insurgent group waging a 22-year rebellion for an independent Islamic state in Mindanao.
Police have blamed them for five nearly simultaneous bomb attacks in Metro Manila on Dec. 30 that killed 22 people and injured nearly 100 others.
Government officially charged with murder last week several ranking MILF leaders for the bombings and suspended peace negotiations that were to begin this year.
Talks collapsed last year when the military launched a major offensive against the rebels, leading to the fall of the MILF’s main enclave, Camp Abubakar, in Maguindanao.
But President Estrada had offered to relaunch peace talks this year. Chief peace negotiator Edgardo Batenga said backchannel dialogues with the MILF will continue in the hope of reviving the talks.
The military said MILF rebels have stepped up their attacks following the bombings. Last Sunday, MILF guerrillas attacked several Army detachments in other remote towns in Lanao, triggering fierce clashes but no immediate casualties.
The rebels soon freed the two workers, apparently due to pressure by pursuing Army troops.
The businessman, Steven Chua, and his two workers were seized at gunpoint by the rebels near a wharf in Tawi-Tawi’s island-town of Sitangkai, said Col. Hilario Atendido, spokesman of the Armed Forces’ Southern Command.
The rebels and their captives traveled aboard a motorboat to nearby Simunul Island, where they freed the workers as government troops gave chase, Atendido said. The rebels then brought Chua to an undisclosed place.
In April last year, the Abu Sayyaf kidnapped 21 Western vacationers and Asian workers from the Malaysian dive resort of Sipadan and brought them to Sulu. They later abducted several other people, including foreign journalists.
The military began massive assaults against the Abu Sayyaf last September to rescue the remaining hostages and neutralize the extremist group.  Roel Pareño, John Unson, Paolo Romero