Nine men arrested in Indonesia's South Sumatra province in connection with a cache of homemade bombs were flown to Jakarta in blindfolds and shackles under heavy security on Thursday.

The unidentified suspects were arrested in connection with the discovery of some 20 makeshift bombs in the attic of a rented house in Palembang, South Sumatra, on Tuesday, a police source said.

Members of the US and Australian-trained Special Detachment 88 anti-terrorism squad were involved in the raid on the house in the provincial capital, police said.

An AFP reporter saw the men - wearing hoods, blindfolds and handcuffs - being transferred from a plane onto police buses at a civilian airport in the capital.

One of the suspects wore a T-shirt with a logo that said "Suicide."

They were escorted by heavily armed, masked plain-clothes police and taken to a police headquarters on the southern outskirts of the city.

National police spokesman Abu Bakar Nataprawira confirmed that an unspecified number of arrests had been made in relation to the discovery of the bombs but he could not provide further details.

"The suspects will be brought to Jakarta (on Thursday) for questioning," he said.

"There have been arrests but the details about who they are and what they have done will be announced later today."

Local residents told the Antara news agency that the occupants of the house had moved in only two months ago and rarely socialised with neighbours.

One of the suspects was a Singaporean who had been arrested on Saturday, the Kompas daily reported.

It said 16 of the bombs found in the house were primed and ready to be detonated.