Colombo: An international rights group implored the UN on Friday to send observers to help protect civilians in Sri Lanka's civil war when European truce monitors depart following the collapse of the country's 2002 ceasefire.

Sri Lanka's government officially notified peace-broker Norway late on Thursday it is pulling out from the truce with Tamil Tiger rebels, and the Norwegian-led monitoring team later announced the end of their mission.

The imminent departure of European monitors from Sri Lanka highlights the need for a UN human rights monitoring mission, the New-York based Human Rights Watch said in a statement yesterday.

"The Sri Lanka Monitoring Mission was deeply flawed, but its monitors helped to minimise abuses against civilians," said Elaine Pearson, the group's deputy Asia director. "Now the need for a UN monitoring mission is greater than ever."

The Norwegian-brokered ceasefire becomes invalid from January 16 or 14 days after the government's formal notice to the Norwegians. The government has said growing violence over the last two years has rendered the agreement irrelevant.

Norway warned the violence raging in Sri Lanka will likely worsen, and the United States said it was "troubled" by the Sri Lankan government's decision.

"All parties to the conflict share the responsibility to protect the rights of all of Sri Lanka's people," State Department spokesman Sean McCormack said.