The attacks killed 202 people, including 88 Australians.
Australia’s Deputy Prime Minister Richard Marles said it was a difficult day for those who lost loved ones in the bombings.
He told the Australian Broadcasting Corp. that his government had advocated against Patek’s early release and would urge the Indonesian government to ensure he was under constant surveillance while on probation.
Indonesian authorities have said Patek, 55, was successfully reformed in prison and will use him to influence other militants away from terrorism.
Home Secretary Clare O’Neil said it was a horrible day for the victims and their families.
“This is a person who was in the Indonesian justice system. My personal view is that her actions are inexcusable and completely abhorrent,” O’Neil told the National Press Club in Canberra. “We don’t control the Indonesian justice system, and that’s the way the world works.”
Bombing survivor Peter Hughes, who testified at Patek’s trial, said he and other survivors were skeptical that the bomber was a different man.
“There is a story of people like him, they do not stop. Letting him out is laughable,” Hughes told ABC.
Another survivor, Jan Laczynski, said he was shocked and horrified by Patek’s release.
“I still can’t understand how this person who caused so much loss of life, and not just to 88 Australians, 202 people, was able to walk free this morning,” he told Channel 9.
Lawmaker Chris Bowen said Patek’s release was concerning, but the Australian government respected Indonesia’s legal system.
“Indonesians and Australians were killed by these terrible murders, Indonesians and Australians went through this ordeal together,” he told ABC.
Patek was a leading member of Jemaah Islamiah, which was blamed for the explosions at two Kuta beach nightclubs. He was found guilty by the West Jakarta District Court of helping to build a car bomb that was detonated by another person outside the Sari Club in Kuta on the night of October 12, 2002.
Moments earlier, a smaller bomb in a backpack was detonated by a suicide bomber at the nearby Paddy’s Pub nightclub.