Militant cleric Abu Bakar Bashir jailed for the Bali bombings which claimed 202 lives is to have his sentence reduced.
Bashir is the alleged spiritual head of al Qaeda-linked terror group Jemaah Islamiyah.
He is among 53,000 inmates who are to receive a sentence reduction to mark Indonesia's Independence Day on Wednesday.
Mayun Mataram, of the Ministry of Justice and Human Rights in Bali, said: "Convicts with a record of good behaviour can get up to 10-months remission."
He was jailed for 30 months in March for conspiracy in the Bali bombings in 2002.
Prosecutors, who had demanded an eight year sentence and could have asked for the death penalty, were angry about the light sentence.
Survivor Peter Hughes, of Perth, Australia, said: "This is not justice. These guys are criminals and murderers who should be given heavy penalties without a reprieve."
The father of UK victim Daniel Braden said it would allow Bashir to continue "spreading his poison".
Daniel, 28, from Brighton, was visiting Bali on tour with his rugby team when the bomb exploded at the Sari nightclub.
His father Alex said: "I think there is a feeling about Bashir that he should be incarcerated and shouldn't be given the oxygen of publicity - he should not be allowed to continue to spread his poison."
Attorney Wirawan Adnan, who represented many of the Bali bombers including Bashir, said his clients deserve a break just like any other well-behaved inmate, Sky News reports.
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