Military jets and helicopters buzzed over the Sri Lankan countryside Saturday, searching for Tamil Tiger rebels believed to have assassinated the country's foreign minister. The killing has sparked fears of a return to civil war.

Though the government has not taken steps to break a three-year-old cease-fire with the Liberation Tigers of Tamil Eelam, officials from around the world urged both sides to press ahead with the country's faltering peace process and respect the truce.

Foreign Minister Lakshman Kadirgamar was shot by snipers Friday evening at his home. Kadirgamar, 73, an ethnic Tamil who led efforts to ban the Tigers as a terrorist organization but who later backed peace efforts, was wounded in the head and chest, and died after midnight.

The government declared a state of emergency and soldiers scoured the capital, searching homes and stopping cars.

"It is a grave setback to the peace process," an official who leads government peace efforts, Jayantha Dhanapala, told reporters.

The rebels' political chief denied any role in the killing and criticized officials for "hastily blaming" the group.

"We also know that there are factions within the Sri Lankan armed forces operating with a hidden agenda to sabotage the cease-fire agreement," said S.P. Tamilselvan. He urged the government to thoroughly investigate the killing.

Sri Lankan officials were skeptical.

"We find it extremely difficult to accept the denial," government spokesman Nimal Siripala de Silva told reporters. "It's very, very difficult to accept."

Secretary of State Condoleezza Rice denounced the assassination as "a vicious act of terror."

Tamils take part in a religious parade along a road in Colombo. The slain foreign minister was a Tamil who led efforts to ban the rebels before the 2002 cease-fire.Kadirgamar was shot on Friday.