Chief judge Muhammad Saleh said Bashir "has been proven to take part in subversion with the aim of overthrowing the government."

But he added: "There is not enough evidence to say that the defendant Abu Bakar Bashir is the leader and the organiser of subversion with the intention of overthrowing the government."

The five judges, who took turns reading the verdict, said there was no proof that Bashir heads the Jemaah Islamiyah (JI) terror group but added that he was part of its struggle.

Prosecutors had said Bashir heads the al-Qaeda-linked JI, which is blamed for a string of deadly blasts, including last October's Bali bombing.

They said he waged a JI terror campaign to topple the Indonesian government and to establish an Islamic state and had demanded a 15-year term.

Judges also convicted Bashir of an immigration offence. The four-year term includes the sentence for this crime.

They ruled that the time Bashir has already spent in custody be deducted from the sentence. He was arrested last October.

"Just because I am fighting for Islamic Sharia law I am accused of subversion," said a calm-looking Bashir, 65, after the sentence was announced.

"I cannot accept this and I state that I will appeal."

JI is blamed for a string of bloody attacks, including Indonesian church bombings which killed 19 people on Christmas Eve 2000, the Bali blasts last October 12 which killed 202 people and last month's Jakarta hotel blast that claimed 12 lives.

Bashir was not accused over the Bali blasts. His indictment accused him of approving the Christmas Eve attacks, a foiled bombing campaign in Singapore, and an aborted plot to kill Megawati Sukarnoputri before she became president.