Peace monitors began work in Indonesia's Aceh province as fresh violence erupted between troops and separatist rebels despite a ceasefire pact this month.

Rebels blew up an army truck and opened fire at soldiers in an ambush Thursday at Kuta Makmur in North Aceh, said military spokesman Major Eddi Fernandi. The soldiers were on their way back from picking up stores and were not in search of Free Aceh Movement (GAM) rebels, Fernandi said.

"The GAM members had been expecting us and they fired from the hill," he said on Friday. He said the army truck was badly damaged when three bombs placed under a bridge which the vehicle was passing exploded. A soldier was seriously wounded.

A local GAM spokesman, Tengku Jamaica, said the rebels had acted in self-defense because the troops were out to hunt them. "It would be foolish if we did not take any action. We don't want to die in vain," he said.

The clash prompted hundreds of local residents to seek refuge at a polytechnic in Lhokseumawe some 20 kilometers away, witnesses said.

The Joint Security Committee, set up following the signing of the peace pact on December 9, held its first meeting at a hotel in this provincial capital to discuss a working agenda.

The committee is made up of representatives from the government, the rebels and international mediators representing the Geneva-based Henry Dunant Center (HDC). It is charged with monitoring the implementation of the peace agreement, investigating violations and setting up demilitarized zones.

The 15-member panel, whose top international member is a Thai general, will be backed by about 150 monitors – a third from the Indonesian military or police, another third from the rebels and an equal number from the Thai and Philippine military.