On Saturday, three bombs tore through restaurants packed with evening diners, two at outdoor seafood restaurants on Jimbaran beach and one at a steak bar at Kuta beach in an area surrounded by shops and jammed with pedestrians, including children, police said.
At least 107 people were wounded.
Indonesia's health minister said 25 people died in the blasts. Fifteen bodies have been identified - 12 Indonesians including a six-year-old boy, two Australians and a Japanese.
The wounded included 68 Indonesians, 20 Australians, six South Koreans, four Americans and four Japanese, with other nationalities unknown.
Asked whether the blasts on the resort island were bombings in which the attackers killed themselves, the head of the counter-terrorism desk at the office of the chief security minister said: "Indications lead that way. We found heads detached from their bodies and all of them were around the area of the blasts."
Ansyaad Mbai said he did not know whether the bombers wore explosive vests or carried the devices.
An Indonesian security source told Aljazeera's correspondent in Indonesia that the blasts were carried out by bombers who died in the explosions.
Security experts said the strikes bore the hallmarks of Jemaah Islamiyah (JI), a network seen as the regional arm of al-Qaida.
Police blame JI for the 2002 blasts on the same resort island that killed more than 200 people and a series of attacks against Western targets in the world's most populous Muslim nation.
Sources told Aljazeera that mafia
groups may be behind the blasts
However, the correspondent quoted other Indonesian sources as rejecting any linking of Saturday's blasts to Muslim groups.
They believe the incident was a challenge by organised crime groups that sought to stop the Indonesian president's attempts to fight corruption, Aljazeera's Suhaib Jasim said.
A forensics team picked through the debris in the Jimbaran area on Sunday. Chairs and tables had been blown apart, but the buildings appeared largely undamaged.
The nearly simultaneous explosions come almost three years after JI operatives bombed nightclubs in Bali, killing 202 people, most of them foreign tourists.
The latest attack occurred as Bali's tourism-dependent economy was recovering from the earlier blasts, which scared off many visitors.
Saturday's blasts appeared smaller than the 2002 attack, which included a car bomb that flattened its main nightclub target and ripped into buildings for blocks.
President Susilo Bambang Yudhoyono has branded Saturday's attacks as acts of terrorism and vowed to catch those responsible.
Sidney Jones, an expert on Indonesian terrorism and militant organisations with the International Crisis Group, said that with evidence that the bombers killed themselves in the attacks, the situation pointed towards involvement by Malaysians Azahari bin Husin and Noordin Top, alleged key members of JI blamed for attacks in the past.
President Susilo has vowed to
track down those responsible
Some have speculated the attacks could have come from others seeking to destabilise Susilo's presidency or those upset with massive fuel price increases his government pushed through days ago.
"We are disappointed that this could happen again in Bali, a tourist zone that we are proud of. With this the work of the intelligence [agencies] comes under question," said Parliamentary Speaker Agung Laksono, whose Golkar Party has generally supported Susilo.
But Ken Conboy, a Jakarta-based security expert, said earlier that it was difficult to prevent such attacks. "It's just a very hard place to protect if you look at where they hit."
Bali is Indonesia's most popular
Jones added: "You think how open Bali is and how impossible it is to effectively secure beach area. I just don't see that even if they have intelligence ... that you could have prevented it."
Bali, 960km east of Jakarta, is Indonesia's most popular destination for foreign tourists.
Neighbours such as Australia and Singapore offered the Indonesian government help after Saturday's blasts.
Australian Prime Minister John Howard said Indonesia had sought help from Australian police and that victim identification experts were on their way to Bali.