NEW DELHI, OCT. 7 -- Tamil guerrillas lashed out at Sinhalese civilians across Sri Lanka's troubled Eastern Province overnight, killing at least 150 people and creating a mood of near despair in the island nation, according to reports from Colombo, the Sri Lankan capital.

Villages were attacked, a train stopped and set ablaze and individuals pulled from their houses in the upsurge of violence, one of the bloodiest in the five-year civil conflict.

The killings followed the apparent suicide deaths of at least 11 Tamil guerrillas Monday while they were in detention in an Army camp in northern Sri Lanka.

Immediately after the suicides, the main Tamil guerrilla group, the Liberation Tigers of Tamil Eelam, killed six captive Sri Lankan soldiers, four policemen and two employes of a government cement plant.

Sri Lankan President Junius Jayewardene canceled his trip to Canada for next week's meeting of Commonwealth heads of state. He has been under pressure from within his ruling party over the July 29 accord he signed with India seeking an end to the violence between the island's Sinhalese majority and Tamil minority.

Jayewardene said 10,000 people have fled to the Eastern Province port of Trincomalee to seek shelter from violence in the countryside.

As part of the peace accord, India has sent 14,000 troops to Sri Lanka as a peace-keeping force. Indian officials in New Delhi said these units have been instructed to "take all necessary measures" to contain the wave of violence. A spokesman expressed "deep shock and revulsion" at the killings.

Indian officials have given similar assurances in the past, however, and so far the Indian peace-keeping units have failed to stop two outbursts of mass violence: one last night and another a few weeks ago, when guerrillas of the Tamil Tigers wiped out members of rival Tamil groups.

Under the peace accord, the Sri Lankan Army is confined to barracks in contested areas and Tamil guerrillas are required to turn in their arms.

"There is universal concern here, and things are very tense," said a diplomatic source reached by telephone in Colombo. "People are close to despair. No one knows what the {Tamil Tigers have} in mind and no one sees a way out."

According to reports from Colombo, 59 Sinhalese were slain in the Batticaloa district, many of them pulled from houses where they had been living for years alongside Tamil neighbors.

A Sri Lankan military spokesman said Tamil Tiger militants stopped a train from Batticaloa to Colombo last night, set the cars on fire and forced the passengers to get off. The spokesman said the guerrillas separated the Sinhalese from the other passengers and shot 40 Sinhalese to death.

Twenty Sinhalese bus passengers in Amperai district were reportedly gunned down or hacked to death, and another 27 Sinhalese settlers were killed in a coastal village near Trincomalee.