Amnesty International says Sri Lanka is not credibly investigating torture allegations leveled against security forces.

The London-based rights group said Monday that despite having anti-torture legislation in place, a special police investigation unit reportedly carried out only three prosecutions in 14 years.

It says most cases involving torture never go to trial, with such abuse carried out by police, prison guards and military personnel.

The rights group says those suspected of being members of the Tamil Tiger rebel group have been arbitrarily detained without charge for prolonged periods of time and also subject to torture.

Amnesty International says its report comes on the eve of the United Nations Committee Against Torture's review into Sri Lanka.