Jemaah Islamiyah, a Southeast Asian militant group inspired by Al-Qaeda, stands accused of suicide bombings last week in the Indonesian capital where it has mounted a string of attacks in recent years.
JI's ultimate goal is to unite Indonesia, Brunei, Malaysia, Singapore and the southern Philippines into a fundamentalist Islamic state, using terrorist attacks to destabilise governments across Southeast Asia.
In its latest handiwork, two suicide bombers posed as guests before detonating powerful devices in crowded public areas at the JW Marriott and the Ritz-Carlton hotels in an upmarket business district of Jakarta.
"We confirm that the attackers are from Jemaah Islamiyah because there are similarities in the bombs used," national police spokesman Nanan Soekarna told a press conference Sunday.
"They are from the same school. We found similar tools, similar materials and similar methods," he said, adding that nine people were killed and 55 injured in Friday's blasts.
Foreign Minister Hassan Wirayuda had earlier put the toll at eight, including four foreigners and the two bombers.
JI, whose name means "Islamic community", has its roots in Darul Islam, an organisation 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.
It is also blamed for Christmas Eve 2000 bombings that targeted churches and priests, killing 19 people, and an August 2003 attack on the JW Marriott 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.
The Indonesian security ministry's anti-terror chief, Ansyaad Mbai, has said that evidence from Friday's blasts points to Malaysian-born extremist Noordin Mohammed Top, who leads a violent splinter faction of JI.
Sidney Jones, a terrorism analyst with the International Crisis Group in Jakarta, also said Noordin could be involved in the latest carnage.
"Noordin is no longer acting in the name of JI. He's a splinter of JI," she said.
Jemaah Islamiyah was nurtured by Indonesian cleric Abu Bakar Bashir and his countryman Hambali, also known as the "Osama bin Laden of the East," while they were in exile in Malaysia.
Hambali, an Afghan war veteran, was arrested in Thailand in 2003 on suspicion of being both a top Al-Qaeda and JI operative, and taken into 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.
Along with Noordin, several top JI militants are still at large, including Zulkarnaen, reportedly the Al-Qaeda pointman in Southeast Asia, and bomb experts Dulmatin and Umar Patek.