Canberra – Indonesian soldiers sent to quell religious rioting on Ambon worsened the violence because they were not trained in non-lethal crowd control, the US-based Human Rights Watch said Wednesday.

A report by the group released in Canberra said there was no question an extremely grave security threat existed on the island following weeks of fighting between Christians and Muslims. But the report found the troops sent to halt the killing had only added to the problem.

"When they finally did intervene, they shot lead bullets rather than attempting to use any methods of non-lethal crowd control," the report said.

"From February 14 onwards, most of the deaths took place when security forces, whose numbers by March had risen to 5,000 on an island of about 350,000, began implementing shoot-on-sight orders."

Indonesian aid organisations estimate 200 people have died in the communal violence with more than 30,000 forced to leave their homes after churches, mosques and houses were set alight.

The report called on Indonesian authorities to investigate allegations of bias made by both the Christian and Muslim communities.

"Muslims have accused Christian Ambonese police personnel of taking part in attacks against them," the report said. "Likewise, the Christians have accused troop reinforcements of siding with Muslim villagers in several clashes."

The report said Indonesian press reports, senior political figures and diplomats believed the violence was provoked by rogue military officers linked to former President Suharto, with the aim of disrupting Indonesia's June national elections.

But Ambonese community leaders believed the violence was locally instigated. "In either case, the government of Suharto's successor, Habibie, seems to have been half-hearted about investigating allegations of provocation either at the national or the local level," it noted.

But the report said imposing a state of civil emergency on Ambon should be avoided at all costs. "With the very clear exacerbation of the situation caused by the presence of security forces with shoot-on-sight orders, additional measures that allow the military to bypass normal civil rights safeguards are likely to make things even worse."