Jakarta – A human rights group in Papua province said Thursday it was being sued by Indonesia's powerful military for alleging that troops carried out an ambush which killed two Americans in August 2002.

The Elsham group said the military was demanding 50 billion rupiah (5.8 million dollars) in damages in the civil case and an apology published in local and international media.

On Wednesday a witness in the case alleged that Elsham had bribed him to implicate Kopassus special forces in the attack, Antara news agency reported.

Decky Murib told the hearing in the provincial capital Jayapura that Elsham had reneged on promises of money and overseas trips in return for his claims that he had seen the incident. "I feel I have been cheated. That's why I reported this to the Timika district court," Murib was quoted as saying.

Two US teachers and an Indonesian colleague were killed when unidentified gunmen fired on a convoy carrying employees of the US-owned Freeport gold and copper mine.

The US Federal Bureau of Investigation has joined investigations into the attack. US legislators have demanded a full accounting of the incident before any moves to resume military-to-military relations with Indonesia.

In November 2002 Papuan police said Murib had told them that he knew the names of four of 11 soldiers involved in the attack. They said Murib had been an informer and guide for Kopassus.

Elsham denied it had promised Murib cash or overseas trips. "That is entirely untrue. We are human right workers," its deputy director Aloy Renwarin told AFP. "We conducted the investigation in a professional manner. Decky told us that he saw the incident but now he gave a different statement. What's going on?"