Switzerland has condemned "in the strongest terms" what it calls the "odious" assassination of Sri Lanka's Foreign Minister Lakshman Kadirgamar.
Despite a state of emergency being declared in Sri Lanka, the Swiss foreign ministry hoped the peace process would not be derailed by the "absolutely unjustifiable" crime.
The Swiss foreign ministry expressed its "deep consternation" on Saturday and hoped that those responsible for the murder would be quickly identified and brought to justice.
Kadirgamar, 73, was shot in the head and heart at about 11pm (1700 GMT) on Friday by a suspected sniper at his central Colombo home. He died in the National Hospital after midnight.
The Swiss also called on all parties to do everything possible "to avert a potential escalation of tension and to protect the the ceasefire" between the government and the Liberation Tigers of Tamil Eelam (LTTE).
The LTTE began fighting in 1983 for a separate homeland for ethnic Tamils, claiming discrimination by the majority Sinhalese. The conflict killed nearly 65,000 people before a Norwegian-brokered ceasefire in 2002.
The ministry added that Foreign Minister Micheline Calmy-Rey had expressed her sadness and concern after the death of her counterpart.
The two ministers had met most recently on January 4 in Colombo. Calmy-Rey had visited Sri Lanka after the December 26 tsunami devastated the region.
Tamils in Switzerland made a sharp-worded announcement. "The fatal attack on the foreign minister is not an isolated act that could trigger off civil war once again," said Anton Ponrajah, president of the Swiss Association of Tamils.
More significant, Ponrajah added, is that in recent months hundreds of politicians and Tamil intellectuals have been killed.
He believed that behind these attacks were the army or a Tamil group supported by the government.
President Chandrika Kumaratunga declared a state of emergency, empowering authorities to detain without charge anyone suspected of taking part in terrorist activities and to search and demolish buildings.
The government said it had not taken any action that would violate the ceasefire with the Tamil Tigers.
The Tamil Tigers however denied any involvement in Kadirgamar's killing, pro-rebel website tamilnet.com reported on Saturday.
The LTTE political wing leader S.P. Thamilselvan condemned the country's military for "hastily blaming the ... Tigers" for the shooting.
Thamilselvan said the government, which the LTTE accuses of helping a renegade faction wage a war against it in the island's east, should look inwardly for the culprits.
"We ... know that there are sections within the Sri Lankan armed forces operating with a hidden agenda to sabotage the ceasefire agreement," Thamilselvan told the website.
Kadirgamar was instrumental in getting the Tigers outlawed as a terrorist organisation by the United States and Britain and was long seen as a prime target.
A team of more than 100 elite commandos and soldiers stood guard around him everywhere he went. It was not immediately clear how his killer found a window.
The police have blamed the Tigers for the killing, but the government stopped short of accusing them.
swissinfo with agencies
Switzerland has been heavily involved in the peace process in Sri Lanka.
The Tamil community in Switzerland numbers around 40,000.
Sri Lanka's Foreign Minister Lakshman Kadirgamar, a harsh critic of the Tamil separatists, was fatally shot on Friday evening.
Sri Lanka declared a state of emergency following the assassination.
Sri Lanka's Tamil Tiger separatists have denied any involvement in the killing.
Switzerland has condemned the "odious" assassination.