While the heavy firing of Tuesday night and Wednesday has ceased, both sides have vowed to retaliate if attacked again. If violence halts, diplomats say peace talks may still be possible. If not, many fear the 2002 ceasefire may collapse completely.

A suicide bomb attack that killed 10 and wounded the army commander on Tuesday was followed by air strikes on Liberation Tigers of Tamil Eelam (LTTE) territory in the east. The United Nations says thousands have fled their homes.

The pro-rebel website Tamilnet (www.tamilnet.com) quoted Tiger northeastern political chief S. Elilan as saying the rebels awaited instructions from their leadership, but any retaliation would be "catastrophically disabling and devastating to our enemy".

Army spokesman Brigadier Prasad Samarasinghe said there had been no new military action overnight, but that an army camp near rebel territory in the northeast had been fired on with small arms. He would not say if that would prompt retaliation.

Police said a blast at a police station in the north central province wounded eight officers, but that it appeared to be a criminal act not linked to the Tigers.

The border crossings were closed by the army in the aftermath of the suicide attack in Colombo, effectively cutting off the northern government held enclave of Jaffna. They reopened early Thursday, the army said.

The Tigers say more than 12 civilians were killed in the government air and artillery strikes on their territory around the northeastern port of Trincomalee. They also say some 40,000 people have fled their homes.

Aid workers say that figure is probably an overestimate, but the United Nations High Commissioner for Refugees (UNHCR) said it believed thousands had been displaced and called for a halt in hostilities to allow aid to reach them.

Diplomats and analysts say recent suspected Tiger attacks on the military and Sinhalese majority civilians were aimed at creating a backlash they hoped would win them international sympathy and drive more ethnic Tamils to their cause.

Some feel the Tigers, whose two decade fight for a Tamil homeland in the north and east has killed more than 64,000 people on both sides, feel they have not achieved enough from peace and are looking for a reason to restart the conflict.

Others say they have more limited goals and are angry the government has done nothing to rein in renegade ex-rebels, the Karuna group, who Nordic truce monitors say have been operating from government territory and attacking the mainstream rebels.

The reasons the rebels gave for pulling out of peace talks in Geneva is more mundane still -- a dispute over the transport of eastern rebel leaders to a pre-talks meeting. Mediator Norway and the truce monitors are still trying to overcome that hurdle.

In an official statement, the Tigers said the bombing and ongoing killings of Tamil civilians amounted to "attempted genocide", and called for the international community to condemn and immediately stop the attacks.

"The terror atmosphere that has been created throughout the Tamil homeland has shattered the Tamil people," said a statement on their official website. "Today, Tamil people are seeking and expecting protection from our movement."