COLOMBO, March 31, 2008 (AFP) - An international panel invited by Sri Lanka to observe the government's probe into human rights abuses shut down operations on Monday, three weeks after accusing Colombo of failing to tackle the issue.

The International Independent Group of Eminent Persons (IIGEP) was formed to observe an inquiry into 16 cases of serious rights violations, including the August 2006 massacre of 17 local employees of the French charity, ACF.

The panel said Monday in a statement that they were halting their efforts to determine whether the inquiries were being conducted 'in accordance with internationally accepted norms and standards.'

Earlier this month, the panel had accused the government of lacking the political will to investigate the incidents and said Sri Lankan authorities did not meet the basic minimum standards in investigating serious rights abuses.

The IIGEP's final report is expected to be presented to Sri Lankan President Mahinda Rajapakse next month and the panel's office will formally close on April 30, the group said.

Key international personalities, who were earlier invited by Rajapakse to observe the inquiry proceedings, have since left the island.

Colombo has come under fire for its rights record, with Human Rights Watch saying recently that at least 1,500 people -- mostly ethnic Tamils living in the island's restive north and east -- had 'disappeared' between 2006 and 2007.

The New York-based rights group said Sri Lanka was one of the world's worst perpetrators of 'disappearances' and abductions, and described the situation as a 'national crisis.'

Sri Lanka's cabinet last week approved a plan to enact laws to protect witnesses to crimes and to encourage them to testify in cases of abductions and disappearances.

International concern over the human rights situation in Sri Lanka has been mounting amid the government's escalating war against the Tamil Tiger rebels.

Tens of thousands of people have been killed since the Tigers launched their campaign in 1972 to carve out a separate Tamil homeland in the Sinhalese-majority island.

Fighting has stepped up since January, when Colombo formally pulled out of a six-year-old truce with the Tigers.