The United Nations and the United States have strongly condemned the assassination of Sri Lankan Foreign Minister Lakshman Kadirgamar who was gunned down late Friday in the capital city of Colombo.
UN Secretary-General Kofi Annan condemned "in the strongest of terms this criminal and senseless act," announced his spokesman Stephane Dujarric.
"The secretary-general hopes that this tragedy will not weaken the commitment of the people of Sri Lanka to achieving a durable peace in the country," the spokesman said at UN headquarters in New York.
The United States also denounced the murder, demanding the perpetrators be "brought to justice."
US Secretary of State Condoleezza Rice said in a statement: "I am shocked and saddened by the assassination of Sri Lankan Foreign Minister Lakshman Kadirgamar. This senseless murder was a vicious act of terror, which the United States strongly condemns. Those responsible must be brought to justice."
The United States and Britain are among the five countries where the Tigers remain on the terror list.
Norway, which is mediating between the government and the rebels, deplored the killing as "a big blow" to the ceasefire and to the stalled peace process in the country.
The assassination came as "a big, big blow to the ceasefire and the whole peace process irrespective of who is behind this," said Norway's chief truce monitor Hagrup Haukland.
Kadirgamar, a Tamil, was in the forefront of Sri Lankan government's campaign for an international ban on the Liberation Tigers of Tamil Eelam (LTTE) rebels. He was shot at around 11:15 p.m. local time (1715 GMT) after taking a swim at home and died of heart and head injuries at 00:15 a.m. Saturday (1815 GMT).
Despite his efforts to outlaw LTTE internationally, the 73-year-old slain minister had strongly supported a negotiated settlement since a Norway-brokered ceasefire was in place in Feb. 2002, according to Sri Lankan officials.
"Minister Kadirgamar was a person who has done so much for the country. He has done a yeoman service to the peace process," Justice Minister John Seneviratne said.
The high-profile murder has raised fears of an escalation of tensions which could lead to the resumption of civil war.
On Saturday, President Chandrika Kumaratunga declared a state of emergency, while police blamed the Tamil rebels for the killing.
"A state of national emergency has been declared to facilitate enhanced security measures and effective investigations of this act of wanton terror, " said a statement from Kumaratunga's office.
Police Inspector General Chandra Fernando said, "It's the Tigers. We suspect it's them."
The killing occurred a day after the Tigers warned of a comeback to civil war unless the government stopped backing a splinter faction attacking them in the east of the island.
The Tamil Tigers began fighting in 1983 for a separate homeland for ethnic Tamils in the country's north and east. Post-truce peace talks have been stalled since 2003 over rebel demands for a wide autonomy in this country of 19 million people.