PAGADIAN, Philippines, (AFP)-Islamists mounted simultaneous attacks on six army bases in the southern Philippine island of Mindanao on Thursday, leaving 17 people dead and shutting down a major highway.

Fighting raged into the night along a 25-kilometer (15.5-mile) stretch of the national highway, isolating the towns of Kauswagan, Linamon, Bacolod and Baloi, said military spokespersons and local government officials.

The Moro National Liberation Front attacked the Inudaran army base in Kauswagan at dawn while the Pangayawan and Kaduwalan army posts in Bacolod and the Robokon detachment in Linamon as well as the Lapayan camp in Kauswagan came under attack in the afternoon, said Major Johnny Macanas of the Army's 4th infantry division.

The Matampay army outpost in Baloi also came under siege in the afternoon, he said, adding that several hundred Islamists were involved in the six attacks.

Franklin Quijano, the mayor of Iligan city near Kauswagan, told reporters they were checking reports that one of the two Kauswagan bases under attack had been overrun by the MILF.

Eight armored troop transports roared out of an infantry base in the city of Cagayan de Oro toward Iligan to the west by early evening, residents said.

Quijano said the military and the police have set up "blocking forces" to prevent the fighting reaching Iligan, a city of about 800,000 people which is adjacent to Kauswagan and hosts a major hydroelectric power plant which supplies electricity to the entire island of Mindanao.

Macanas said the fighting left two soldiers and 15 Islamists dead. Most of the Islamist casualties were inflicted by army artillery, he said. Nine other soldiers were wounded, he added.

Islamists attacked the Inudaran base from a training base near the military camp, Macanas said. "We have positively pinpointed the area of the rebels in the jungle and we are going to take over the MILF camp. It will be seized."

The 15,000-member MILF is fighting for a separate Islamic state in the southern Philippines, which is predominantly Christian.

The military have also blamed the MILF for a recent series of bomb attacks on buses and other targets despite continuing peace talks with the government.

Macanas said the flareup of the fighting was apparently the result of the arrest on Monday of MILF guerrilla leader Amonodin Tomarompong, accused of setting off bombs aboard a ferry off the Mindanao port of Ozamiz last month that left 45 people dead.

Meanwhile, four government militiamen were slain and another was wounded in an MILF ambush in the central Mindanao town of Carmen on Wednesday, said a military spokesman, Major Julieto Ando.