Jakarta – The only suspect in the poisoning death of Indonesia's most prominent human rights activist was freed from prison after receiving a month's reduction in his sentence as part of Christmas celebrations, a prison official said Tuesday.

Pollycarpus Priyanto, a 45-year-old pilot, was originally sentenced to 14 years on charges of putting a fatal dose of arsenic in Munir Thalib's food while the human rights campaigner was on a flight from Jakarta to Amsterdam two years ago.

The Supreme Court quashed the conviction in October citing a lack of evidence, but upheld Priyanto's two-year sentence for falsifying flight documents. Priyanto has long maintained he was innocent in Munir's death.

Indonesia traditionally cuts prison terms for some inmates on national holidays, and the justice ministry said Tuesday the pilot was one of more than 6,000 non-Muslim convicts to benefit on Christmas.

His one-month reduction made him eligible for release and he left Cipinang prison in the capital, Jakarta, on Monday, said Rosmita, an official at the jail who uses one name.

Activists slammed the decision, saying it showed that President Susilo Bambang Yudhoyono's government was not serious about finding justice for Munir.

"This shows that the government has been halfhearted in finding his killer," said Usman Hamid from Solidarity Action for Munir, who urged that a new fact-finding team be created to probe the murder.

Munir rose to prominence toward the end of Suharto's 32-year dictatorship. He went on to probe killings by Indonesian troops during East Timor's bloody struggle for independence and military-led violence in the separatist provinces of Papua and Aceh.