An Indonesia court is due to hand down its verdict on Thursday against Umar Patek, dubbed 'Demolition Man', for his role in the 2002 Bali bombings, bringing a 10-year probe into the nation's deadliest act of terror to a close.

Patek, 45, is accused of assembling explosives for twin suicide bombings on a bar and a nightclub in Bali that killed 202 people, including 88 Australians, and church attacks in Jakarta on Christmas Eve in 2000 that killed 19.

The West Jakarta district court opened the session at around 9:20 am with more than 100 journalists, many Australian, crammed into a small 12-seater section and some spilling out of the courtroom to hear Patek's fate.

Around 300 police were guarding the courtroom and four snipers stood atop neighbouring buildings, West Jakarta police chief Widodo told agencies.

Patek, dressed in white Islamic attire, sat with his head down in front of a panel of five judges, as one read a detailed description of his charges, which include premeditated murder, illegal firearms possession and bombmaking.

The judges read a long summary of testimony from witnesses who have taken the stand since the trial began in February, carrying on well past noon.

Judge Mirdin Alamsyah recapped one witness describing 'screams and fire everywhere' after the bombings.

Prosecutors are seeking a life sentence -- sparing Patek the maximum penalty of death by firing squad as he has shown remorse during the trial.

The accused claimed he was 'against it from the start' and had tried to stop the attack at the 11th hour. He has also apologised to victims and their families.

Before his arrest, Patek was the most-wanted terror suspect in Indonesia and the United States had a $1 million bounty on his head.

After more than eight years on the run, he was arrested in the Pakistani town of Abbottabad in January 2011, where US commandos killed Al-Qaeda leader Osama bin Laden four months later. He was extradited to Indonesia in August.

Patek has testified that he played a minor role in assembling the explosives and denied having any bombmaking expertise.

But US Federal Bureau of Investigation special agent Frank Pellegrino testified in April that Patek was well known as an expert bombmaker among militants in the region.

Pellegrino said the FBI had collected evidence that Patek planned to kill US troops and suggested he went to Abbottabad to meet bin Laden before his arrest, a claim Patek has repeatedly denied.

Patek is the last suspect detained in Indonesia to be tried for the attacks.

"Indonesians and the international community have long waited for this case to be over," prosecutor Bambang Suharyadi said last month.

The 2002 Bali bombings triggered a long crackdown on terrorism in Indonesia, focused on weakening the Al-Qaeda-linked Jemaah Islamiyah (JI) terror network blamed for the bombings.

Anti-terror squads trained by Australian and US police have conducted bloody raids, killing Dulmatin and Noordin Mohammed Top, suspected of helping orchestrate the attacks, and Malaysian Azahari Husin, an alleged bombmaker.

Indonesia also executed three men in 2008 -- Imam Samudra, and brothers Amrozi bin Nurhasyim and Ali Ghufron, known as Mukhlas -- for playing major roles on the ground in the operation.

Several others have been jailed, including bombmaker Ali Imron, who was given a life sentence for helping build and deliver bombs.

The only suspect yet to be tried is Riduan Isamuddin, known as Hambali, who allegedly helped orchestrate the attacks and has been detained at the US naval base at Guantanamo Bay since 2006, accused of having financial links to Al-Qaeda.