Jemaah Islamiyah, the Islamic militant network blamed for a string of attacks in Southeast Asia and inspired by Al-Qaeda, is fighting to create a pan-Islamic state in the region.
At least nine people were killed and more than 40 injured on Friday when bombs exploded at two luxury hotels in Jakarta, the capital of Indonesia -- where JI sealed its notoriety with the 2002 Bali bombings, which killed 202 people.
Officials said it was too early to say whether Friday's attacks were the work of Islamic militants, but suspicion is likely to fall on JI, which uses terrorist attacks to destabilise regional governments.
JI's ultimate goal is to unite Indonesia, Brunei, Malaysia, Singapore and the southern Philippines into a fundamentalist Islamic state.
The group, whose name means "Islamic community," has its roots in Darul Islam, a group which fought for an Islamic state in Indonesia in the 1950s and 1960s and survived a military defeat in the 1960s.
JI has carried out more than 50 bombings in Indonesia since April 1999, according to the Brussels-based International Crisis Group, including the 2002 Bali bombings and similar attacks on the resort island in 2005 that killed 20.
The group is also blamed for Christmas Eve 2000 bombings that targeted churches and priests, killing 19 people, and the August 2003 attack on the JW Marriott hotel in Jakarta -- again struck on Friday -- that left 12 dead.
A suicide car bomb outside the Australian embassy in Jakarta in September 2004 killed 10 people.
JI is also suspected of involvement in bombings in the Philippines, where its followers have attended training camps, and of bomb plots in Thailand and Singapore.
If the organisation is confirmed as the perpetrator of Friday's bombings in Jakarta, it would be its first major attack since the 2005 bombings in Bali.
JI was nurtured by Indonesian cleric Abu Bakar Bashir and his countryman Hambali, who is also known as Riduan Isamuddin and the "Osama bin Laden of the East," while they were in exile in Malaysia after fleeing Suharto's Indonesia.
Hambali, an Afghan war veteran, was arrested in Thailand in 2003 on suspicion of being both a top Al-Qaeda and JI operative. He is currently in detention at the US prison camp in Guantanamo Bay, Cuba.
Bashir, the alleged spiritual head of JI, was jailed in March 2005 for involvement in a conspiracy that led to the 2002 Bali nightclub bombings but was released the following year. His conviction was later overturned on appeal.
Self-proclaimed JI leaders Zarkasi and Abu Dujana, arrested on Indonesia's Java island in June 2007, were each sentenced to 15 years in prison in April 2008.
Several top JI militants are still at large, including Malaysian-born former accountant Noordin Mohammad Top, the alleged mastermind of the 2002 Bali bombings who is believed to be running a radical JI faction.
Zulkarnaen, reportedly the Al-Qaeda pointman in Southeast Asia, also remains on the run, along with bomb experts Dulmatin and Umar Patek.
Sidney Jones, a terrorism analyst with the International Crisis Group in Jakarta, said Indonesia's handling of the executions last November of three men convicted of the 2002 Bali attacks had increased the threat of reprisals.