Umar Patek — who was jailed for 20 years over his role in the 2002 Bali bombings — has been given a further five-month reduction to his sentence as part of Indonesia's Independence Day celebrations. 

Australian Prime Minister Anthony Albanese said the decision would add to the "distress and trauma" of victims' loved ones coming up to the 20th anniversary of the attack that killed 202 people, 88 of them Australians. 

Here's what we know.

Who is Umar Patek?

Patek was accused of being the expert bombmaker for Jemaah Islamiyah (JI), a South-East Asian terror network linked to Al Qaeda.

Evidence in his 2012 trial suggested former Al Qaeda leader Osama bin Laden gave JI $30,000 to wage jihad and Patek might have met him in a Pakistani town, a claim Patek repeatedly denied.

He went into hiding after the bombings, being on the most-wanted terrorist list in several countries, with the US offering a $1 million bounty for his head. 

Patek was eventually captured in Abbottabad, Pakistan, in 2011 and extradited to Indonesia. 

On top of his conviction over the Bali bombings, he was also found guilty of weapons and conspiracy charges over a terrorist training camp in Aceh in 2009, and for mixing explosives for a series of Christmas Eve attacks on churches in 2000.

Local media reports said Patek has been participating in a de-radicalisation program for several years.

In 2015, Major General Agus Surya Bakti — who led the Indonesia's de-radicalisation efforts through its anti-terrorism agency — spoke of Patek's success in the program. 

"It's an extraordinary thing," he said. 

What was his role in the bombing?

Bombs went off at the Sari Club and Paddy's Bar in Kuta about 11pm on October 12, 2002. 

Patek made some of the bombs used in the attack, with local media calling him "Demolition Man" during his trial. 

He admitted mixing as much as 50 kilograms of the explosives and packing them into filing cabinets used to carry the bomb to the Sari Club.

During his trial, Patek downplayed his role in the terror plot and argued that he didn't know how the bombs would be used.

What do we know about his sentence?

Patek was convicted for premeditated murder.

He was spared the death penalty because he cooperated with investigators and and apologised to the victims' families, eventually being sentenced to 20 years in prison.

The ABC understands he has been granted routine remissions in his sentence, which has brought his release date forward to 2029. 

Typically, with incremental reductions and good behaviour, prisoners can get parole after serving about two thirds of their sentence. 

He was due to become eligible for parole in January. 

When might he walk free?

There are reports he could be freed within days — but that's only if he is granted parole. 

The ABC has been told that terrorists aren't usually eligible for parole.

And Indonesian authorities say no decision has been made on whether he will be released.

If he's not granted parole, he'll be in prison until 2029. 

Is Australia doing anything about this?

On ABC Breakfast, Mr Albanese said his government was in contact with Indonesia about this, but didn't go into specifics:

What about other people involved in the attack?

In 2008, Imam Samudra, Amrozi, and Mukhlas were executed for their roles in the attack. 

Abu Bakar Bashir — who was found guilty of conspiracy over the Bali bombings — was released from prison after 26 months in 2006 after his sentence was shortened.

He was given a 15-year jail sentence in 2011 for supporting militant training camps, but was released last year. 

As former military commander of JI, Aris Sumarsono — better known as Zulkarnaen — was accused of masterminding the attacks. 

In January, he was sentenced to 15 years in prison on a string to terror charges, but was unable to be tried in relation to the Bali bombings because the statue of limitations had expired.