Protection Urged for Sri Lanka War Crimes Witnesses

International rights groups have demanded protection for potential Sri Lankan witnesses at a U.N.-mandated war crimes investigation into the island's ethnic war which ended five year ago.

Six organizations in a joint letter expressed alarm over alleged intimidation, threats and reprisals against those likely to engage investigators probing the bloody finale to Sri Lanka's Tamil separatists war.

The letter published Tuesday on the website of the Geneva-based International Commission of Jurists urged "meaningful steps" to protect those who cooperated with the war crimes probe which was approved by the U.N. Human Rights Council in March.

"Human rights defenders in Sri Lanka face widespread intimidation," the letter said adding that it could intensify ahead of the presentation of an update on the investigation at the council's September and March sessions.

Sri Lanka has made it clear that it will not grant visas to U.N. investigators.

Colombo says it will also not accept the authority of the U.N. Human Rights Council to probe charges that Sri Lanka's military killed 40,000 civilians in the final months of the war in 2009.

The open letter, also signed by Amnesty International, said they were "deeply concerned" about ongoing attacks against rights activists in Sri Lanka.

"We are alarmed to learn of intimidation, threats and reprisals against all those perceived as likely to engage with and provide information to the investigation mandated by the U.N. Human Rights Council...," the letter said.

U.N. Secretary General Ban Ki-moon and other leaders have urged Colombo to cooperate with the UN rights body after ending a prolonged separatist war that pitted ethnic minority Tamil rebels against the largely Sinhalese army.

Outgoing U.N. rights chief Navi Pillay earlier this month suggested that her staff investigating allegations of mass killings may not have to travel to Sri Lanka at all.

She said there was a "wealth of information" outside the country.

Colombo maintains that its troops did not commit war crimes while crushing the Tamil Tiger rebel movement at the end of a conflict which lasted more than three decades and claimed more than 100,000 lives.