GENEVA - The UN Human Rights Council on Thursday launched an inquiry into alleged war crimes in Sri Lanka, a move angrily rejected by Colombo as counter-productive.

In a 23-12 vote, the council backed a Western-sponsored resolution saying it was time for a “comprehensive investigation into alleged serious violations and abuses of human rights and related crimes by both parties in Sri Lanka”.

Colombo has come under pressure over alleged war crimes committed in 2009 when it launched its final offensive to end one of Asia’s deadliest civil wars.

The UN has said up to 40,000 Tamil civilians may have been killed during the last months of fighting against Tamil Tiger rebels and blamed many of the atrocities on government forces, a charge Colombo vehemently denies. Sri Lankan President Mahinda Rajapakse, who has tightened his grip on power since crushing the rebels, said the UN probe would only do harm. “We reject this,” Rajapakse told AFP in Sri Lanka. “This resolution only hurts our reconciliation efforts. It does not help.”

Sri Lanka’s UN ambassador Ravinatha Aryasinha called the rights council’s move a “serious breach of international law”, telling the council it constituted “an infringement of state sovereignty and pre-judgement of the outcome of domestic processes.” The proposal for a inquiry was put to a vote after failed attempts by Sri Lanka’s supporters Russia, Cuba and Pakistan to use procedural grounds to block it.

And China’s delegate called it an “example of the politicisation of human rights”, saying Sri Lanka needed “time and space” to heal the wounds of the past. But US Secretary of State John Kerry hailed the decision. “Today’s vote in the UN Human Rights Council sends a clear message: the time to pursue lasting peace and prosperity is now; justice and accountability cannot wait,” he said in a statement. Amnesty International also welcomed it.

“The UN inquiry brings new hope for the thousands of victims of abuses in Sri Lanka,” said David Griffiths, its Asia-Pacific deputy director, saying Colombo had twice ignored calls by the council to conduct an independent probe. “Now they have a fresh opportunity to restore some international credibility by cooperating with the investigation,” he said.

Sri Lanka’s critics also spotlight what they say are ongoing rights violations. “The human rights situation in Sri Lanka continues to deteriorate, despite some areas of limited progress,” US envoy Paula Schriefer told the council. She highlighted concerns over sexual violence, enforced disappearances, extrajudicial killings, torture, violations of the rights to freedom of expression, association and peaceful assembly, and threats to judicial independence and the rule of law.

She also cited intimidation of and reprisals against human rights campaigners, lawyers and journalists, and attacks on minority groups, including Muslims, Christians, and Hindus. But Aryasinha said such allegations were biased, and fueled by pro-Tiger activists around the world. “Such biases and extreme ideologies ignore the ground realities, the legitimate aspirations of the Sri Lankan people, and trivialise the price paid by all Sri Lankans to defeat a 30-year brutal terrorist conflict and consolidate peace,” he said.

British ambassador Karen Pierce rejected that claim. “We sympathise with all those Sri Lankans who suffered at the hands of the brutal Tamil Tigers. No one regrets that they were defeated. But the response to any believed terrorist threat should be proportionate, to avoid fuelling the fires of extremism,” she said. On Wednesday, UN rights chief Navi Pillay had told the council that it was crucial to recall the “magnitude and gravity” of the violations allegedly committed by both the government and the rebels, notorious for their suicide bombings.

The 1972-2009 conflict claimed 100,000 lives, according to a UN estimate.

The resolution specifically tasked Pillay’s office with investigating events between 2002 and 2009 - a time-frame criticised by Sri Lanka as being too short, but which its critics said was the period covered by the country’s own truth and reconciliation process. The initial results of the probe are to be submitted to the council in September.