Abu Bakar Bashir is regarded as the spiritual leader for radical militants in Indonesia, but the white-bearded 71-year-old has always denied involvement in terrorism.
The softly spoken Muslim preacher, who was arrested on Monday, served almost 26 months for conspiracy over the 2002 attacks on Bali nightspots that killed 202 people, before being cleared and released in 2006.
Bashir was active in the early 1960s in several Islamic student organisations at Al-Irsyad University in his home town of Solo, Central Java, before founding in 1972 the Al Mukmin Muslim boarding school at nearby Ngruki.
He and close friend Abdullah Sungkar, both of Yemeni descent, were jailed by the Suharto regime from 1978 to 1982 for inciting people to reject the secular national ideology in favour of an Islamic state.
They fled to Malaysia in 1985 when the Supreme Court granted a prosecution appeal for a longer sentence. It was there, according to prosecutors, that they officially founded Southeast Asian terror group Jemaah Islamiyah (JI) in 1993.
Sungkar died in 1999, a year after Bashir returned to Indonesia following Suharto's downfall.
From 2000 he devoted more and more time to the Indonesian Mujahideen Council, an umbrella group which he heads and which seeks sharia law.
Two years after his release from prison in 2006 he founded Jamaah Ansharut Tauhid (JAT) as a legitimate -- although radical -- body with which to continue agitating for Islamic law and jihad, or holy war.
"Let us strengthen Islamic brotherhood with one single aim, that is to uphold the Islamic sharia to help this state and nation," he said in 2006, showing that prison had not dampened his fiery support of Islam.
International Crisis Group expert Sidney Jones predicted in a report published in July that Bashir's arrest would not have a significant impact on the jihadist movement in Indonesia.
"He has numerous critics among fellow jihadis who cite his lack of strategic sense and poor management skills," Jones said.
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