Jakarta – Almost all witnesses to a massacre of civilians in Indonesia's Aceh province last year said the army was to blame, an international rights group reported Friday.

"Virtually all witnesses asserted that the Indonesian army was responsible, although they could not name individual perpetrators," said Human Rights Watch, in a report focusing on the killing of 30 men and a two-year-old child at a plantation in East Aceh in August.

Human Rights Watch (HRW) said the evidence was given to two visiting commissioners of the Indonesian National Commission on Human Rights (Komnas-HAM) two weeks after the killings.

The New York-based group in a statement sharply criticised Komnas-HAM for failing to actively pursue an investigation into what it called one of the worst massacres in post-Suharto Indonesia.

"The Indonesian government in general and Komnas-HAM in particular have failed dismally to investigate serious human rights abuses in Aceh," said Sidney Jones, HRW Asia director, in the statement. "And Komnas-HAM has gone from being the most credible institution in the country to being a real hindrance to human rights progress."

The Free Aceh Movement (GAM) has been fighting since 1976 for an independent state in Aceh on Sumatra island. Countless civilians have died since then, in addition to rebels, police and soldiers. Each side accused the other of the plantation massacre, in which a group of ethnic Acehnese was lined up and executed by a group of armed men in camouflage uniforms.

HRW said the Komnas-HAM team in Aceh failed to follow up important leads and allowed military officers to accompany them on some interviews. "After their return to Jakarta, the commissioners sat on their findings for five months. Only on January 8, 2002 did Komnas-HAM agree to set up a formal commission of inquiry but more than two months later, no progress was evident."

HRW urged the government to give highest priority to ensuring the perpetrators of the massacre are brought to justice. It called on parliament to hold hearings into why so many serious human rights violations in Aceh remain unsolved.