In a statement issued in Colombo, the group identified several Tamil politicians who it said were at "immediate risk" of assassination by the Tigers.

They include Rajavarothiyam Sampanthan, an MP and secretary-general of the Tamil United Liberation Front (TULF), as well as Veerasingham Anandasangiri, the TULF vice-president.

It said the Tigers had repeatedly called on these people to resign or face the consequences, and added that they had received "threatening letters and phone calls in the name of the LTTE (Liberation Tigers of Tamil Eelam) or front organisations."

Amnesty called for an international campaign to put pressure on the Tamil Tigers not to attack people who take no direct part in Sri Lanka's civil war.

Geneva Convention

It said it was appealing to the Tigers on the basis of the Geneva Convention, which forbids attacks on non-combatants.

Amnesty said that although some Tamil politicians had been given government protection, this did not alter their civilian status.

The Tigers were widely blamed for the killing of TULF member and MP, Neelan Thiruchelvam, in July.

He was blown up by a suicide bomber while on his way to work.

Neelan Thiruchelvam was a key figure in on-going efforts to find a solution to the conflict in Sri Lanka.

An adviser to President Chandrika Kumaratunga, he had been working on a devolution plan for the Tamil community, which was opposed by the separatist Tamil Tigers

The Tamil Tigers have been fighting for a separate homeland for minority Tamil population in Sri Lanka's north and east since 1983.