Jakarta  - An Indonesian district court on Wednesday unexpectedly acquitted a former senior intelligence official of charges of murdering a prominent human rights activist.

The South Jakarta district court declared Muchdi Purwoprandjono "not guilty" of involvement in the assassination of Munir Said Thalib, who died of arsenic poisoning aboard a Garuda Indonesia flight to Amsterdam in 2004.

The panel of judges argued the prosecutors failed to provide evidence to back up the charges that Muchdi ordered the assassination of Munir, an outspoken government critic.

"The panel of judges declared the defendant not legally and convincingly proven guilty of the crime of ordering the murder of Munir ... (and) cleared the defendant of all charges," said Chief Judge Suharto, reading the court's ruling.

Suharto, who like many Indonesians goes only by one name, said Muchdi should be immediately released from detention.

On December 2, government prosecutors formally sought a 15-year jail sentence for Muchdi, 59, a former military Special Forces general and deputy head of the State Intelligence Agency.

The verdict sparked outrage among Munir's supporters who argue that Muchdi deserves life in prison. But legal experts said it reflected the weakness of the evidence.

During the court proceedings, all witnesses for the prosecution - many of them intelligence officials - either failed to materialize, or have retracted statements they provided to police during initial investigations, claiming they were pressured during questioning.

The prosecutors had to rely only on the circumstantial evidence of records of 40 telephone calls between former Garuda Indonesia pilot Pollycarpus Budihari Priyanto and Muchdi in the period leading up to Munir's murder.

Pollycarpus is now serving a 20-year jail sentence after the Indonesian Supreme Court in January found he laced Munir's orange juice with arsenic. Former Garuda chief Indra Setiawan was also jailed for one year for his role in the murder.

Muchdi was the first senior official to face trial for the murder.

Indonesian human rights activists have long suspected that the intelligence agency was behind the murder of Munir, 38, one of Indonesia's most outspoken human rights activists who challenged abuses committed by the regime of dictator Suharto.

Munir's widow, Suciwati, told reporters outside the court that she would respect the ruling but expected prosecutors to file an appeal to a higher court. (dpa)