police have made their first arrest following the October 1 triple
suicide bombings in Bali, detaining a man named "Hassan" during a
raid in East Java.
The breakthrough came on Sunday night, eight days after triple suicide blasts ripped though three crowded restaurants in Jimbaran Bay and Kuta, killing 23 people, among them four Australians and three suicide bombers.
"This person is strongly suspected of having links with the Bali blasts," deputy national police spokesman Soenarko Ardanto said.
"But he is still a suspect and we have seven days to question him."
Soenarko said the man, a construction worker he called only "HS" but who police sources named as Hassan, was arrested late on Sunday in the village of Jember.
Soenarko said the man allegedly shared a rented room with one of the bombers ahead of the attack.
A police source also told AAP the man stayed with one of the suspected bombers in a maze of alleys close to police headquarters in the Denpasar suburb of Dangin Puri Kaja.
The man was sent back to Bali at 1.30am on Monday morning following his arrest, Soenarko said.
The arrest came as police moved the three death-row ringleaders of the 2002 Bali bombings to a high security jail because of security concerns at their Denpasar prison.
It also came ahead of Wednesday's third anniversary of the October 12, 2002 bombings in which 202 people died, including 88 Australians.
So-called "Smiling Assassin" Amrozi bin Nurhasyin, Imam Samudra and Mukhlas - all awaiting firing squads - were moved on Tuesday from Bali's Kerobokan Prison to Batu Prison on Nusakambangan, an island off the south Java coast, Bali justice ministry spokesman IG Rata told AAP.
The high-security jail is home to former Indonesian dictator Suharto's son, Tommy, who is serving a 15-year sentence for masterminding the murder of a supreme court judge.
"They were moved for security reasons," Rata said, adding that the order for the transfer had come directly from Indonesian Justice Minister Hamid Awaluddin in Jakarta.
"The soil at Kerobokan and the walls are too fragile and the prison is too full," he said.
"There is only capacity for 338 prisoners there but there are now more than 800 in there."
In all, five of the Bali bombers were moved, all wearing hoods, Rata said.
Batu Prison, about 250 kilometres south-east of Jakarta, is known as Indonesia's "Alcatraz". The jail is home to the country's most dangerous criminals.
The overcrowded Kerobokan Prison is where Australian convicted drug smuggler Schapelle Corby is serving her 20-year jail term and also houses the so-called Bali Nine, whose trials for alleged drug trafficking began on Tuesday in Denpasar.
Indonesian police have questioned the three death row bombers over the recent triple suicide blasts in Kuta and Jimbaran, which killed 23 people.
Balinese protesters were expected to rally outside Kerobokan prison on Wednesday to demand the immediate execution of the trio.
Security has been tightened on the holiday island following the bombings and ahead of the anniversary, which will be attended by Foreign Minister Alexander Downer and Australian Federal Police Commissioner Mick Keelty.
Snipers will be deployed on building roofs surrounding a memorial close to ground zero where the blasts tore through the Kuta nightclub strip three years ago, killing 202 mostly foreign holidays makers, including 88 Australians.
Thousands of soldiers, police and intelligence officers have also been stationed at nearby beaches, resorts and businesses, with security blocking off access to the memorial site several hours before the commemoration.