Hundreds of mourners and survivors commemorated Wednesday the 20th anniversary of the bombings that killed more than 200 people on the Indonesian resort island of Bali, as Jakarta considers the early release of one of the attack's masterminds.

Grieving families, attack survivors, and representatives from several embassies will attend a memorial in Bali's popular tourist hub of Kuta, where Al-Qaeda-linked militants detonated bombs at a bar and nightclub on 12 October 2002.

"It's okay that some people have forgotten what happened 20 years ago but there are still real victims, there are children who lost their parents in the bombing," 47-year-old victim Thiolina Marpaung, one of the organizers of the memorial who has left with permanent eye injuries in the attack, told AFP.

"I don't want them to be forgotten."

The candlelight vigil will be held at the site of the attack by victims' family members to mark Southeast Asia's deadliest terrorist attack and remember the 202 victims.

Most were foreign holidaymakers from more than 20 countries but Australia suffered the biggest loss, with 88 dead.

Australia's prime minister told a memorial service in Sydney Wednesday that the horror of the bombings was swiftly countered by incredible acts of self-sacrifice and bravery.

"They sought to create terror, but people ran towards the terror to do what they could for friends and strangers alike," Prime Minister Anthony Albanese told a crowd gathered under light rain at the city's famous Coogee Beach.

Some 88 doves were released during the memorial — one for each Australian killed.

Albanese said the Bali bombings had left a permanent mark on Australia's national identity, in a similar fashion to the devastating Gallipoli campaign of World War I.

In Bali, the Australian consulate there will also have a memorial service, where Indonesian President Joko Widodo will address families by video and former Australian prime minister John Howard will deliver speeches.

Local militant group Jemaah Islamiyah, linked to Al-Qaeda, was blamed for the bombings, which took place at two popular night spots that accounted for all the victims. Another device exploded harmlessly outside the US consulate.

All the leading perpetrators of the Bali attacks were either executed, killed by police, or jailed.

But the Indonesian government is considering an early release for Bali bombmaker Umar Patek. He has only served half of his 20-year sentence.

Jakarta has held off freeing him after angering Australia and victims' relatives who say his pending release has caused fresh trauma before they marked the anniversary.