Officials and security experts say the bombings Saturday night on the Indonesian island of Bali bear the hallmarks of Jemaah Islamiyah, which has carried out similar attacks across Southeast Asia.
The latest attacks come nearly three years after J.I. militants carried out a similar series of bombings on the island. That attack killed 202 people, mostly foreign tourists.
Australian Foreign Minister Alexander Downer, whose country lost nearly a hundred people in the 2002 bombings, says Saturday's incident appears to be the work of J.I.
"You can assume that this was the action of J.I. or some like organization. And given that the bombings appear to be coordinated, it seems to be quite clearly a terrorist attack," he said.
Since the shadowy, al-Qaida-linked Islamic militant organization first hit the headlines in 2001, several J.I. militants have been arrested and some have been sentenced to death for a spate of terrorist acts. They include the 2002 Bali bombings, the 2003 J.W. Marriott hotel explosions in Jakarta and last year's car bombing outside the Australian Embassy in Jakarta.
But security officials and experts say the arrests failed to deal a fatal blow to the organization, which wants to establish an Islamic state across predominantly Muslim areas of Southeast Asia. Two key members, Malaysians Noordin Mohamed Top and Azahari Bin Hussin, remain at large. Both are believed to be highly skilled in explosives.
John Harrison, a terrorism expert at the Institute of Defense and Strategic Studies in Singapore, says in some ways the successful arrests in previous attacks have made it harder to stop J.I. entirely.
"J.I. has become more difficult to contain largely because counter-terrorists have been very good at breaking up the network and putting pressure, so that the network we once knew as J.I. has fragmented and because of that they have been much more difficult to penetrate and identify and they are a much more fluid organization," he said.
Some security experts say J.I. is no longer operating a traditional command-and-execute structure. Rather, they say, cells and individual militants now act independently.
But J.I.'s targets remain the same: places frequented by Westerners. Saturday's attacks on Bali took place in restaurant areas with a largely foreign tourist clientele.
Security officials note that Saturday's attack was smaller than the 2002 bombings that targeted packed nightclubs.
Mr. Harrison says this could show J.I.'s ability to cause destruction has been curtailed.
"The fact that it is not of the size of the scale of the devastation of the original Bali bombings that it would tend to suggest that there's is a loss of capability within the group," he said. "If in fact that J.I. has fragmented it would be very suggestive that they would not have the access to the weapons and capabilities to launch major attacks against hard targets."
Last month, Indonesian President Susilo Bambang Yudhoyono warned of fresh terrorist attacks, noting that J.I. had previously struck during the second half of the year. But he did not specify an imminent threat or particular target.
Indonesia's neighbors have been quick to rally behind Jakarta in this latest tragedy. Southeast Asian countries stepped up security after the attacks and have pledged to continue to help Indonesia fight terrorism.
The U.S. government, through its embassy in Jakarta, says it will work with the Indonesian government to defeat the terrorists. It also warned its citizens that there is still a possibility that Americans and other foreigners may still be a target of attack in Indonesia and the rest of Southeast Asia.
J.I. militants are believed to operate across the region, sneaking through porous maritime borders. The group has carried out attacks in the Philippines and had planned to bomb Western targets in Singapore, including diplomatic missions.