A man who has admitted involvement in the Bali bombings has told investigators the three explosions happened simultaneously only by accident, Indonesia police have said.

Ali Imron (centre) said he felt happy after the bombing

Suspect Ali Imron, who was arrested this week in East Kalimantan province, said the two main blasts in the attack went off prematurely.

Police have also said it was now thought unlikely that a suspect killed in the attacks was a suicide bomber, as had been suspected.

After the attack on 12 October, analysts pointed to the apparent co-ordination of the blasts as evidence that it was a sophisticated and minutely-planned operation.

Timing

Ali Imron has told police that the two bombs at the bars in Kuta were somehow triggered prematurely by a smaller blast near the US consulate in Denpasar.

That disputes the sequence of events given by Australian Federal Police (AFP) who are assisting in the investigation.

AFP reports that the bomb at Paddy's went off first, at about 2315 local time, followed within 10 to 15 seconds by the Sari nightclub blast and then 45-60 seconds later by the bomb in Denpasar.

Mr Imron, the younger brother of two other men held in connection with the attack, was arrested along with another suspect on Monday.

Police say he has admitted to driving the van used to carry the bomb to Paddy's Bar and to taking part in planning meetings.

Bali bomb case

At least 17 detained Nine more sought First trial could take place in February

Profiles of the main suspects

Zainuri Lubis, a spokesman for the investigation team, said on Thursday that Mr Imron also assembled the bombs.

Mr Lubis said the suspect told police he was surprised that all the bombs exploded simultaneously.

"In fact he set the bombs himself for several minutes apart," Mr Lubis said.

As soon as he heard about the explosions, Mr Imron went directly to a mosque to pray. "When asked how he felt, he said he was happy."

'Accident'

Mr Lubis also said a suspect who died in the blast in Paddy's Bar was not now believed to be a suicide bomber.

Iqbal, who is believed to have carried a bomb into the bar, became involved in an argument with a woman there which delayed his departure from the scene. If Mr Imron's account of the timing is true, then Iqbal would not have expected the bomb to go off so soon.

"We suspect (his death) was an accident," Mr Lubis said.

Monday's arrests bring the number of people detained in connection with the attack to at least 17.

More than 190 people - mainly foreigners - were killed when two bombs tore through a nightclub district in Kuta last October.

Police are searching for nine more men they have named as suspects.