Umar Patek, accused of involvement in the 2002 Bali bombings in which 202 people died, arrives in court on Monday.
Patek, 45, is accused of making the bombs that ripped through Bali nightclubs packed with tourists in 2002.
He is also accused of mixing chemicals for 13 bombs that detonated in five churches in Jakarta on Christmas Eve 2000, claiming 15 lives.
In court, Patek said he didn't know the purpose of the bombs in Bali, and that he was not involved in planning the attack.
He said that he was "only asked to help Mukhlas," a militant who was executed in 2008 after he was found guilty for masterminding the Bali bombings.
After the legal proceedings, Patek expressed his regret to those in the courtroom.
He said that he felt remorse for the Bali bombing, but downplayed his involvement in the incident, claiming that he was forced to take part in it.
He offered his apologies to the families of those who were killed.
The Bali bombings were a watershed for Indonesia, which has the world's largest Muslim population, forcing the state to confront the emergence of an increasingly vocal militant minority.
Court is set to adjourn on May 21.
Sarah Sheffer, Reuters
