Security is tightening for Abu Bakar Bashir's next outing from prison, as police consider questioning the cleric about his relationship to the Jakarta terror attack.
The radical cleric, notorious in Australia as the spiritual leader of Jemaah Islamiah, the group behind the Bali bombings, will appear in court on Tuesday seeking an early release from jail.
But his case has been hijacked by the Jakarta terror attack, carried out by assailants who had trained in the paramilitary training in a camp in Aceh, North Sumatra, which Bashir is in jail for supporting.
About 1800 police and military personnel will secure the town of Cilacap, Central Java, with expectations of hundreds more vocal supporters turning out for the prosecution's response.
Indonesian National Police spokesman Agus Rianto says the court process must be allowed to continue, although Bashir will be questioned if it will aid the investigation into the Jakarta attack.
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"Regarding judicial review trials, that's an existing lawful mechanism and we must respect that process," he said.
"The result is all up to the judges, we don't want to presume."
Bashir was sentenced to 15 years for supporting the camp, which trained Jakarta attackers including Afif, 32, a gunman who was pictured wearing a black T-shirt and shooting police with a chillingly calm demeanour.
Afif was sentenced to seven years' jail for his underground training and released in 2015 after authorities were satisfied with his behaviour in jail.
Bashir's lawyers deny Afif ever visited him in jail, but terror observer Al Chaider told AAP he knew of three meetings, in November and December last year.
Bashir's lawyer Mahendradatta says the 77-year-old is upset about being linked to the Jakarta attack.
He also denies that Bashir knows Bahrun Naim - believed to be the brains behind the assault, which claimed four civilian lives and four attackers.
Bahrun Naim is thought to be with Islamic State (IS) in Syria, and jostling for leadership of radicals in Southeast Asia.
In 2014, Bashir pledged allegiance to IS with supporters in prison, but his lawyers say he has since retracted the pledge.
In court this month, the cleric gave a long defence of his decision to back the Aceh camp, arguing it was a religious obligation.
The court may call up to five witnesses on Tuesday, including terror convicts from Nusakambangan, the prison island where Bashir is held.
It's said Afif and Bahrun Naim were followers of terror convict and IS supporter Aman Abdurrahman, who police have already removed from Nusakambangan for questioning in Jakarta.
