Jemaah Islamiah (JI), a South East Asian militant group with links to al-Qaeda, has a long track record of bomb attacks in Indonesia and elsewhere in the region.
The most deadly were the near simultaneous blasts in two Bali nightclubs in Bali on 12 October 2002, which killed 202 people.
JI and affiliated cells have also been implicated in attacks against Christian targets in eastern Indonesia, a suicide bombing outside the Australian embassy in Jakarta in September 2004, and a similar strike at the JW Marriott hotel, also in Jakarta, in August 2003.
Since the Bali bombings, scores of militants associated with the group have been jailed or killed.
In January 2012, the Philippines military said it had killed two key leaders of the group in a raid in the south of the country.
Those reportedly killed were Malaysian Zulkifli bin Hir, or Marwan, who in recent years had become one of the most-wanted militants in the region, and Mohammad Ali, alias Muawiyah.
JI - whose name means Islamic Group in Arabic - is said to have been formed by a handful of exiled Indonesians based in Malaysia in the late 1980s.
It has its roots in Darul Islam, a radical movement that called for the establishment of Islamic law in Indonesia.
The network grew to include cells across the region, including in Indonesia, Malaysia, the Philippines, Singapore and Thailand.
Its goal is the establishment of an Islamic state across South East Asia. In its formative years JI advocated using largely peaceful means to pursue this goal, but in the mid-1990s the group took on a more violent edge.
This growing militancy was said to be nurtured in part through contacts between JI figures, and senior al-Qaeda members in Afghanistan.
Under the influence of al-Qaeda, JI embraced the idea that its goals could only be secured through a "holy war".
But some JI members became unhappy at the disproportionately large number of unintended Muslim victims of the bombing campaign.
Indonesian security analysts say the organisation later split into two broad factions - bombers and proselytisers, with the latter attempting to steer the organisation towards using preaching as its main weapon.
Adding to these internal divisions was the sustained pressure applied to JI by Indonesian security agencies, often in concert with foreign counterparts, notably from the US, Australia and other South East Asian states.
This pressure has led to the killing or imprisonment several key JI leader and the arrest of more than 200 suspected members across the region.
Abu Bakar Ba'asyir, said to be one of founders of JI but who later reportedly renounced violence, was sentenced to 15 years in jail in June 2011. The term was later reduced to nine years.
Logistics chief Riduan Isamuddin, also known as Hambali, was arrested in Thailand in 2003 and is now in US custody in Guantanamo.
Senior bomb maker Fathur Rahman al-Ghozi was killed by police in the Philippines in 2003, and bomb-making expert Azahari bin Husin was shot dead by police in Java in 2005.
In September 2009, Indonesian officials confirmed the death of Malaysian JI member Noordin Mohamed Top. Australian forensic experts had implicated him in both the 2003 Marriott and the 2004 Australian embassy attacks.
In February and March 2009, several suspected militants were arrested in a series of raids in the mountains of Aceh province, where officials said groups with possible links to JI had training camps.
Those arrests were followed by the killing by police of Dulmatin, the last of the Bali bomb suspects to face justice or death, the following year.
The war in Afghanistan in the 1980s allowed relationships to develop between JI members and the future core of al-Qaeda, including Osama Bin Laden.
However evidence suggests that although some JI personnel might be inspired by the larger global mystique of figures such as Bin Laden, the South East Asian group remains operationally and organisationally distinct.
JI also has links with other violent South East Asian Islamist groups, mainly as a result of their simultaneous presence at training camps in Afghanistan.
These include the Moro Islamic Liberation Front (MILF), a secessionist movement fighting for a Muslim homeland in the southern Philippines, as well as several other Indonesian, Malaysian and Thai groups.