Dulmatin, also known as Joko Pitono and nicknamed Genius, is widely believed to be a senior member of the shadowy Asian militant group Jemaah Islamiah (JI).
Accused of helping plan and execute the bomb attacks in Bali in 2002, he has so far evaded capture and is currently believed to be living in the Philippines.
While he has long been on Indonesia's most wanted list, he now appears to be an important target for the US as well.
A US offer of a $10m reward for
information leading to his death or arrest indicates just how influential officials believe him to be.
Washington gave the same amount of money to Thailand in 2003, for its part in the arrest of Hambali - dubbed by the Central Intelligence Agency as the "Osama Bin Laden" of South East Asia.
Electronics expert
An Indonesian national born in central Java in 1970, Dulmatin originally worked as a car salesman.
The exact time he became interested in militant activity is unknown. But he is widely believed to have been the protégé of Azahari Husin, one of the suspected masterminds of the 2002 Bali attacks and other bombings, who was killed by police in 2005.
Dulmatin is not thought to have had any formal scientific training, but he appears to have gained significant technical skills, supposedly under the guidance of Azahari.
According to the Asia Pacific Foundation, Dulmatin was among the few JI militants able to assemble and explode large chlorate and nitrate bombs.
Dulmatin is also known to have attended a militant training camp in Afghanistan, returning to Indonesia in the mid 1990s, where he is thought to have been a regular visitor at an Islamic school in Solo founded by Abu Bakar Ba'asyir, the man alleged to be JI's spiritual leader.
Ba'asyir was jailed for conspiracy over the 2002 Bali attacks, though he was later cleared of the offence.
Phone bomb
Dulmatin first became internationally known when named as a key suspect for the bomb attacks at two nightclubs in Bali on 12 October 2002.
A total of 202 people died in the attacks, many of them foreign tourists.
He is believed to have set off one of the bombs with a mobile phone, as well as making explosive vests for a suicide bomber and working alongside Azahari to assemble the massive car bomb used in the attacks.
Like Azahari and his suspected accomplice Noordin Mohamed Top, some analysts believe Dulmatin has also been involved in other bomb attacks in East Asia, but there is little direct evidence of this.
In fact, since 2003 he is believed to have been based in the southern Philippines, involved in training other militants at secret camps.
In 2005, he was thought to have been killed in a targeted air strike by the Philippine military, but the information turned out to be wrong.
In January 2007, the Philippines army said he had been injured during a gun battle between troops and Abu Sayyaf militants, though it was not clear if he was seriously hurt.
According to regional analysts, there are fears that Dulmatin and other JI operatives, notably Umar Patek, have formed an alliance with the Abu Sayyaf, the smallest and most radical of the Islamic separatist groups in the southern Philippines.
Abu Sayyaf was thought to be providing protection and assistance to JI, while JI provided bomb-making expertise and training in return.
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