Erwida Maulia, Jakarta – London-based rights group Amnesty International has urged the Indonesian Attorney General's Office (AGO) to initiate a new investigation into the alleged murder of Indonesian rights activist Munir Said Thalib in 2004.

Sixteen country directors of Amnesty signed a letter sent Tuesday to Attorney General Basrief Arief, urging that he make the investigation a priority.

"Although two people have now been convicted of the killing, there are credible allegations that those responsible at highest levels have not yet been brought to justice.

"The lack of accountability in Munir's case contributes to an ongoing sense of fear among human rights defenders in Indonesia," Amnesty says in the letter, a copy of which was sent to The Jakarta Post.

The rights group also criticized the acquittal of Muchdi Purwoprandjono, a former deputy at Indonesia's State Intelligence Agency (BIN), in a court hearing in 2008 in relation to the murder case.

"At the time, human rights groups said the trial did not meet international standards of fairness after key prosecution witnesses retracted their sworn testimonies," Amnesty said.

Amnesty made the call ahead of the seventh anniversary of the death of Munir, on Wednesday.

Munir was found dead on a Garuda Indonesia flight from Jakarta to the Netherlands on September 7, 2004. An autopsy carried out by Dutch authorities showed that he died as a result of arsenic poisoning.