Muslim rebels resisting a major government assault in the southern Philippines abducted then released scores of villagers Thursday as the military kept up fierce attacks that have reportedly left more than 100 dead on both sides.

The offensive against a notorious kidnap group and Moro Islamic Liberation Front guerrillas, accused of harboring the criminals, was quickly spreading from the rebels' stronghold in a vast marshland area to neighboring provinces on southern Mindanao island.

Army Col. Agustin Dima-Ala said about 100 MILF guerrillas attacked an army detachment in the village of Tinumiges in Lambayong town in Sultan Kudarat province, near the Pikit marshland, and abducted 25 residents.

The rebels later withdrew and released the villagers one by one, he said. The fighting left 35 rebels, four pro-government militiamen and three civilians dead, he said.

MILF spokesman Eid Kabalu said 12 rebels were killed.

In a separate incident, army spokesman Maj. Julieto Ando said about 100 residents of Bual village, about 20 miles southeast of Pikit, were trapped inside their homes after scores of rebels burst in looking for food. The rebels abducted eight residents, then set them free a few hours later.

At least four rebels and one civilian were killed as the rebels withdrew toward marshland, the military said.

The fighting began Tuesday with a government assault on the Pikit area, about 575 miles southeast of Manila. The military accused the rebels of sheltering members of the notorious kidnap gang Pentagon, which is on a U.S. list of terrorist organizations.

President Gloria Macapagal Arroyo ordered renewed assaults against the rebels Wednesday after her cease-fire order failed to stop fierce fighting.

The military said at least 122 rebels were killed and scores wounded since the fighting broke out, while acknowledging it suffered four dead and 21 wounded.

"We're being hit and we're hitting back," Ando said. "We are battling these Pentagon criminals, lawless elements, and if these other groups get in the way, we have to take countermeasures against them."

Rebel spokesman Kabalu said 17 of his fighters were killed and six wounded overall, and claimed the guerrillas killed 49 government soldiers. Neither count could be confirmed independently.

As many as 25,000 villagers have sought shelter from the fighting, near the border of North Cotabato and Maguindanao provinces, in schools and other government buildings.