Members of the Thai police, navy and air force are among 15 people being questioned over a string of deadly New Year's Eve bombings in Bangkok, with some having links to anti-government groups, authorities said yesterday.

General Sonthi Boonyaratglin, the leader of the bloodless coup on September 19, refused to say who might have been behind the attacks, other than to say those detained had links to unnamed anti-government forces.

Authorities had earlier said that eight of the 15 detained in raids on Saturday were military officers.

The bombings killed three people and wounded nearly 40 while the capital was in the midst of New Year celebrations.

Whether the joint military-police raids signalled a major breakthrough in the investigation is too early to tell, especially after some of the coup leaders including Sonthi expressed strong caution that apparently did not rule out the possibility of the suspects being scapegoats, observers said.

"I was informed that the bombers are linked to a group of people who are anti-government and committed the bombings to discredit and undermine the stability of the government," Sonthi said before leaving on a trip to China. "I give police a free hand to investigate and will talk with them when I return."

Sonthi said he expected more arrests involving other branches of the military or police soon.

When asked about public speculation that the 15 people in custody could be simply scapegoats, Sonthi said: "Like I said, if so, the police chief has to pay the price."

He added: "The police chief will know how much responsibility he has. And he also has to decide on his own whether what he has done is right or wrong because he must know before going to arrest someone - and this [type of] responsibility is high."

Police chief Kowit Watana has had an uneasy relationship with the coup leaders, and his handling of the Bangkok bomb case could determine his future, sources close to the Council for National Security (CNS) said.

Nearly 100 police officers and soldiers searched 18 locations in Bangkok and its outlying suburbs early on Saturday when they detained the eight military and police officers and seven civilians. None of the suspects has been charged and no further details were released.

Among the locations searched was a community radio station in Lop Buri, just outside Bangkok, where authorities believe the bombs were assembled.

Soon after the bombings, Thailand's powerful military declared that the attacks were staged by politicians and renegade army officers loyal to exiled prime minister Thaksin Shinawatra. But until now it has offered little proof of those allegations. The police, meanwhile, initially seemed to lean toward the theory that southern insurgents were responsible.

General Saprang Kalayanamitr, the CNS secretary, also insisted yesterday that the bomb attacks were politically motivated and had nothing to do with violence in the deep South.

In a hand-written letter faxed while he was travelling in China earlier this month, Thaksin accused the country's ruling authorities of unfairly implying he was behind the violence.

He also said he suspected Islamic separatists in the South could have been responsible for the eight small blasts.

Meanwhile, the Patani United Liberation Organisation (Pulo) yesterday dismissed a news report in The Australian, saying the longstanding separatist organisation had nothing do to with the Bangkok bombings and was not affiliated with Jemaah Islamiyah, the Southeast Asian radical Islamic group affiliated with al-Qaeda.

"If we are repeatedly and falsely blamed with such baseless accusations, then this is surely and purely a pretext to link us with any party unknown to us and to drag us unjustly into an unrelated regional conflict which is of no interest to us," said Kasturi Mahkota, Pulo's foreign affairs chief, in a statement to The Nation.

The Nation, Agencies