The Bali bombing was the work of a well-organised team of up to eight people who may have detonated the deadly blast by remote control, says an Indonesian newspaper quoting local intelligence sources.
The international police hunt for the Bali bombers has focused on a former Indonesian Air Force officer.
And details have emerged on how the attack was carefully planned to kill as many people as possible.
The Washington Post said the former officer had confessed to making the bomb.
He had told Indonesian investigators he regretted the huge loss of life, but had not revealed who told him to make the bomb.
An official said the man learned how to make explosive devices while serving in the Air Force, which later dismissed him for misconduct.
Bali's police chief, Brigadier Budi Setyawan, refused to comment on the report.
A source close to the inquiry told news agency AFP the bombers used a combination of powerful C4 plastic explosive and gas cylinders to kill as many people as possible.
Just before the main blast, they detonated a small bomb to bring people out into the street.
An Indonesian newspaper, the Koran Tempo, said eight professional bombers in two vans detonated the bombs, which tore apart the Sari Club and Paddys Bar at Kuta Beach, killing at least 181 people.
Quoting an unnamed police source in Bali, the Koran Tempo said the bombers appeared to be professional and could have used remote-control devices.
The two vehicles stopped near the popular Sari, causing a traffic jam in the narrow street while clearing a space in front of them, the report said.
One van was left behind and those in it got into the second vehicle, which sped off before the bombs blew up.
The explosive was packed in the van's roof, a police spokesman told Reuters.
Koran Tempo also quoted an unnamed National Intelligence Agency official as saying eight people - seven Indonesians under the leadership of a person from the Middle East - did the bombing.
"They are all already out of Bali," the source said.
Asked about the newspaper report, Brigadier Setyawan appeared to confirm it.
"That is from information gathered from the joint intelligence team," he said, referring to a team linking local and national police, the military and intelligence agencies.
National police chief General Da'i Bachtiar said some of the witnesses who had been questioned spoke of a man who disposed of a white plastic bag and fled when he was hailed shortly before the blast.
The Washington Post said police were still interrogating two other men about the bombing.
Koran Tempo quoted an Indonesian security source as saying the Government had learned a week before the bombing that Muslim extremists were planning an attack.
Security was heightened at 60 locations throughout the country, but not in Bali because officials did not suspect militants would strike the resort island.
Officers from Australia, Britain, Germany, Japan and the US Federal Bureau of Investigation are assisting Indonesian security forces.
Jakarta has taken the unusual step of giving Australian police equal authority in the inquiry.
Canberra is putting up a $2.3 million reward to help hunt down those responsible for the bombing, which killed at least 30 Australians and left 180 missing.
Bali messages and latest information on New Zealanders
New Zealand travellers in Bali, and their families around the world, can exchange news via our Bali Messages page. The page also contains lists of New Zealanders in Bali and their condition.
Foreign Affairs advice to New Zealanders
* Travellers should defer travel to Bali
* NZers in Bali should keep a low profile and remain calm
* Foreign Affairs Hotline: 0800 432 111
Feature: Bali bomb blast
Related links
Bali bombers may be alive
AdvertisementAdvertise with NZME.