Philippine troops recovered the bodies of 14 marines, some beheaded, who had clashed with Muslim insurgents while searching for a kidnapped Italian priest, a marine spokesman said Wednesday.

Nine others were wounded in one of this year's bloodiest fights, which erupted Tuesday in Tipo Tipo town on southern Basilan island, said Lt. Col. Ariel Caculitan.

At least 10 of the bodies were beheaded, including those of six marines earlier reported missing in the gunbattle, Caculitan said.

The military said at least 300 Al Qaeda-linked Abu Sayyaf militants, joined by "lawless groups," ambushed the heavily outnumbered marines.

But Mohagher Iqbal, chief negotiator for the Muslim separatist Moro Islamic Liberation Front, which is engaged in peace talks with the government, said the marines had attacked an MILF stronghold and his forces fought back.

He denied his forces were responsible for the beheadings, but said he would investigate.

Four MILF members were killed and seven wounded in the fighting, he said.

Iqbal accused government troops of violating a 2003 cease-fire, saying they failed to coordinate their movement into the area with the MILF.

He ruled out that Abu Sayyaf militants had sought refuge in the MILF stronghold, but did not say who might have carried out the beheadings.

Abu Sayyaf has beheaded hostages, including an American, in the past.

"It cannot be a mistaken encounter because it was a deliberate act on the part of the marines that entered the area, knowing that the area is a bailiwick of the MILF, in complete violation of the cease-fire," Iqbal said.

Still, he said the clash was only a "tactical problem" and would not hamper peace talks with the government.

Caculitan said the military had no official information that the MILF was involved in the attack -- but that if they were, officials would ask the cease-fire committee to investigate and take appropriate action.

"As of this time, we still maintain that the attackers were composed of mixed forces coming from the (Abu Sayyaf group) and lawless armed groups in the area," he told reporters.

He said there were unconfirmed reports that senior Abu Sayyaf commander Isnilon Hapilon's group was sighted in the area.

Washington has offered a US$5 million (euro3.6 million) reward for Hapilon who has been linked to the abduction of 17 Filipinos and three Americans in May 2001.

Philippine officials have issued conflicting statements on the identity of groups that might have kidnapped the Rev. Giancarlo Bossi, a 57-year-old missionary from Milan, on June 10.

Authorities initially blamed an MILF commander. The group denied any role, and deployed forces to help government troops search for Bossi.

National Security Adviser Norberto Gonzales has said Abu Sayyaf militants may have been responsible. But army officers say Abu Sayyaf gunmen do not have a presence where Bossi was kidnapped.

Caculitan said he could not confirm reports that Bossi was taken to Basilan.