The Liberation Tigers of Tamil Eelam (LTTE) are locked in a low intensity conflict with the military that threatens to rupture a 2002 truce and rekindle a two-decade civil war. They want the government to disarm a breakaway faction led by a former rebel commander called Karuna.

"The government's refusal to rein in armed groups as pledged at (talks in) Geneva has been the primary cause of intensified violence and the stalemate in the peace talks," London-based chief rebel negotiator Anton Balasingham told Reuters in an email interview sent late on Sunday.

"Since the government has outrightly denied the very existence of Karuna group in government controlled areas and refused to disarm them, the LTTE has no choice other than to take the responsibility on itself and neutralise Karuna's armed men."

Karuna, widely viewed as shadowy rebel supremo Velupillai Prabhakaran's top commander before he split with the mainstream Tigers in 2004, has formed a political movement and wants to eventually supplant the Tigers. He refuses to disarm.

"The unbridled violence unleashed against the Tamil civilians by Tamil paramilitaries and the state's armed forces has now become the critical issue overshadowing the peace process," Balasingham said. The government denies the military is helping Karuna, but many diplomats are increasingly sceptical.

The Tigers had been due to attend a second round in talks in Geneva last month, but pulled out indefinitely over a series of issues, from the disarmament of Karuna to transport arrangements for their eastern military leaders, amid a cycle of deadly violence that killed more than 200 people in a month.

"The LTTE will not be able to participate in the peace talks as long as Tamil civilians are systematically eliminated by both Tamil paramilitaries and by the state's armed forces," Balasingham said.

"We feel that it is the responsibility of the state to contain the excesses of the security forces and to rein in the military-backed paramilitaries and to create a congenial situation conducive for peace talks," he added.

Diplomats and analysts fear a return to meaningful talks may now be some way off, with both sides increasingly locking horns over minutiae rather than focusing on the core issue.

The Tigers want wide autonomy and a separate homeland for ethnic Tamils in Sri Lanka's north and east, which President Mahinda Rajapakse has rejected out of hand.

Many fear a rash of land, sea and air attacks over the past month, coupled with an assassination attempt on the island's army commander by a suspected rebel suicide bomber, could be a precursor to deeper violence that could spiral out of control and reignite war.