Despite the assassination of the foreign minister two days ago, the government on Sunday reiterated its commitment to making peace with ethnic Tamil rebels who officials have said almost certainly were behind the meticulously planned killing.

The Sri Lankan government's restraint underscored its limited options for dealing with the rebels, the Liberation Tigers of Tamil Eelam, as well as its fervent desire to avert a resumption of the 20-year civil war that claimed roughly 64,000 lives before the two sides signed a cease-fire agreement in February 2003.

"I will redouble my efforts and the commitment of my government" to seek peace through dialogue, President Chandrika Kumaratunga said in a nationwide television address Sunday night. "We can't let terror and hatred overcome us."

The sniper attack on Foreign Minister Lakshman Kadirgamar in the garden of his private residence late Friday was the latest and most spectacular in an escalating round of political violence -- including a grenade attack on a Tiger political office Sunday -- that some fear has brought the cease-fire to the brink of collapse.

Early this year, things appeared to be moving in a more positive direction, as bitterly divided ethnic factions briefly seemed to forget their differences in the aftermath of the Dec. 26 tsunami, which killed more than 30,000 people in Sri Lanka and decimated its fishing and tourism industries.

About 18 percent of Sri Lanka's 20 million people are Tamils, most of whom are Hindus. Many Tamils have long complained of discrimination at the hands of the predominantly Buddhist and ethnic Sinhalese majority. The Tamil Tigers, as the rebels are popularly known, have been fighting for their own state, known as Tamil Eelam, in northern and eastern Sri Lanka.

On Saturday, the Tigers' political head, S.P. Thamilchevan, denied that the group was responsible for Kadirgamar's assassination and suggested that it could have been carried out by "sections within the Sri Lankan armed forces" opposed to the three-year-old cease-fire, according to TamilNet, a Web site that is generally sympathetic to the rebels.

A government spokesman, Nimal Siripala de Silva, said the Tigers' denial was "very, very difficult to accept."

Analysts and diplomats tend to share that view. They note that the rebels have in the past denied responsibility for high-profile assassinations -- including the 1991 suicide bombing that killed Rajiv Gandhi, who had previously served as India's prime minister -- despite strong evidence to the contrary.

Kadirgamar, 73, was particularly high on the Tigers' list of enemies. As a Tamil in a Sinhalese-dominated government, the Oxford-educated foreign minister was considered a traitor by the rebels, who were also angered by his successful lobbying of foreign governments -- including the United States -- to have them labeled as terrorists.

The killing was carried out with ruthless efficiency. Kadirgamar was shot in the head and chest moments after he emerged from the swimming pool at his private residence in a wealthy neighborhood of Colombo, authorities said. The fatal bullets were fired from the second floor of a residence overlooking the minister's property. Besides spent cartridge casings, investigators found a grenade launcher, candy wrappers and a homemade sniper's tripod with an attached seat.

The assassination sparked a massive manhunt in the capital, where police and military personnel could be seen Sunday afternoon checking identity papers and searching vehicles at checkpoints on major thoroughfares. A dozen Tamils were detained for questioning, authorities said, but there was no indication Sunday night whether any were considered suspects in the killing.

Even before Friday's assassination, tensions had escalated sharply in Sri Lanka, especially in the east, where the Tigers have been fighting what diplomats describe as a "dirty war" with a breakaway faction that the rebels contend is backed by government security forces.

Relations between the government and the rebels have also been strained by the failure to implement an agreement to share international tsunami aid. The accord has been held up by the Supreme Court.

Buddhist monks pay a visit in Colombo to Sugandi Kadirgamar, widow of Lakshman Kadirgamar, the Sri Lankan foreign minister who was shot dead Friday. Officials blame Tamil rebels for the killing, an accusation they deny.