Sri Lanka's air force struck Tamil rebel bases Wednesday in retaliation for a suicide bombing that killed eight people and insurgent attacks on navy ships as the country edged back toward civil war.

The pro-rebel TamilNet Web site said at least 12 civilians were killed by the airstrikes, which began late Tuesday in northeastern Sri Lanka, but the toll could not be independently confirmed. Military spokesman Brig. Prasad Samarasinghe said the strikes hit only rebel bases.

Early Wednesday, Sri Lankan navy ships in the northeast came under rebel attack, and air force jets responded with airstrikes on Tamil Tiger bases around the strategic port of Trincomalee, Samarasinghe said.

"Our navy units have come under terrorist attack this morning and we have retaliated," he said.

The government closed the highway providing the only land link between Sri Lanka's south and Tamil rebel-held areas in the north, said Helen Olafsdottir, spokeswoman for the European team monitoring the country's 2002 cease-fire accord.

Sri Lanka's latest spasm of violence began Tuesday when a suspected Tamil suicide bomber — a woman pretending to be pregnant — blew herself up in front of a car carrying the Sri Lankan army commander. Eight people were killed and 26 wounded, including the commander.

Later that day, the government launched the airstrikes on Tamil Tiger-held areas in the first major military assault since the cease-fire four years ago.

The rebels said the air force had dropped at least 150 artillery shells. They have asked the European cease-fire monitoring group "to clarify whether the Sri Lanka army has launched a full-scale war," TamilNet said, quoting the rebels' Trincomalee commander S. Elilan.

Separately Wednesday, unidentified gunmen shot and killed a prominent Tamil businessman in the northern town of Vavuniya, area police chief Gamini Silva said. Other police officials, who asked not to be named in keeping with police rules, said the businessman was known to be close with Tamil Tiger rebels.

Last week, the rebels backed out of peace talks that had been scheduled to start Monday in Geneva, citing attacks on Tamil civilians and other disputes with the government.

The rebels accuse the Sinhalese-dominated government of discriminating against minority Tamils and want a separate homeland. Before the 2002 truce, more than 65,000 people died in two decades of war. At least 89 people, including 43 soldiers or police, have been killed this month.

Retired Air Marshall Harry Goonetilleke, former head of Sri Lanka's air force, said the country could return to full-scale warfare if the government's military operation expanded and resulted in substantial rebel casualties.

"If the limited operations is limited to certain areas ... it might not escalate," he said. "But if these operations are enlarged and kill substantial number of rebel cadres or their sympathizers, then I think it will lead to full scale hostilities."

The suicide bomber in Tuesday's attack talked her way into a military complex in the Sri Lankan capital, Colombo, after saying she had an appointment at a clinic. She blew herself up in front of a car carrying the army commander, Lt. Gen. Sarath Fonseka, who was in stable condition at a Colombo hospital Wednesday, said Hector Weerasinghe, a hospital director.