Sri Lanka's rebel Tamil Tigers have come under increasing criticism and are accused of using an 18-month old cease-fire in the country's civil war to assassinate and kidnap political opponents.
The latest accusations come from two prominent human rights organizations, Amnesty International and Human Rights Watch. Both groups on Thursday accused the Tamil Tigers of undermining a fragile peace process in Sri Lanka by murdering and kidnapping political rivals with impunity.
The groups say at least 22 people linked to Tamil political parties have been killed since the rebels signed a cease-fire agreement with the Sri Lankan government in February last year.
Amnesty International and Human Rights Watch say there is convincing evidence that the Tamil Tigers have been behind the killings.
The Tamil Tigers have in the past denied involvement in political assassinations.
The latest criticism comes just days after the U.S. State Department called on the Tigers to stop terrorist activities, respect the cease-fire and return to peace negotiations.
The rebels suspended peace talks in April after accusing the government of reneging on earlier promises to develop Tamil areas hard hit by the war. The rebels have yet to respond to a government offer last month to share administrative power in the Tamil-dominated northeast of the country.
The rebels have been fighting for an independent Tamil homeland since 1983, but more recently said they would be willing to negotiate a political solution and settle for political and administrative autonomy.
Some 65,000 people have so far been killed in the conflict, which has devastated Sri Lanka's economy.