The police cannot yet tell who was behind the assassination attempt, Thaksin said, referring to the discovery of a car loaded with explosives parked near his home on Thursday morning.

However, Maj-General Chamlong Srimuang, a leader of the anti-government People's Alliance for Democracy, was not involved, Thaksin said.

Chamlong is an old friend of General Pallop Pinmanee, who Thaksin sacked as deputy director of the Internal Security Operations Command (Isoc) following the arrest of his former driver while entering the car.

Thaksin dismissed speculation that the incident was set up. "Ultimately you will know what it is. Police will prove what the truth is. If it was a set-up, there would not be a culprit," he said.

Asked about his family's concern, Thaksin's face dropped as he replied, "My family is worried. I came home thinking, 'Oh, I have the chance to have dinner with my family'. "This is unbelievable to happen in Thailand," he said.

Thaksin said he was tipped off about an assassination plan on August 9 when he came back from inspecting the Northeast region and again on August 10 after returning from a trip to Cambodia. "I thought it was just threats, but when it happened on Thursday then I knew it was not a threat but real," he said.

Asked if he had talked to Pallop at all before sacking him, Thaksin said he had not spoken to him for a year.

A police source responsible for the ongoing investigation into the matter later said that there were more than 10 individuals involved in the murder plot against Thaksin, including two Army major generals and many colonels.

Apart from their frequent activities in connection with politics, these 10 people were known to have close connections with Army Lieutenant Thawatchai Klinchana, the driver of the explosives-laden car intercepted by police on Thursday.

"But there is no concrete evidence implicating them with the assassination plot.

The suspect, now charged initially with having explosives in his possession, appeared tense and exhausted after police questioned him throughout Thursday night. He kept his eyes closed while being escorted from his detention cell to an interrogation room at the Crime Suppression Division compound yesterday morning.

The suspect put his head in his hands when the questioning began, and asked for two headache tables. He was later allowed to rest in his detention cell after he said he was not feeling well after a long interrogation session.

Police spokesman Pol Lt-General Ajiravid Subarnbhesaj later reiterated that the assassination plot was not a hoax, saying the car that was found loaded with explosive devices on Thursday had also been seen at many other places the premier went to.

He said the premier's security staff had seen the car, which was to have been driven by Thawatchai on Thursday. "The police investigation into the matter has corroborated the observations of the security staff about the car. It was seen at many places where the premier went," the spokesman said.

Ajiravid said Thawatchai insisted he had just been hired to drive the car.

"But when he was confronted with the evidence that the car had left the Internal Security Organisation Command early in the morning, he stopped repeating those claims. He has, however, maintained he was not involved in the assassination plot," he said.

Democrat Party chief adviser Chuan Leekpai yesterday questioned why police jumped to the conclusion that Thursday's incident was an assassination attempt.

"Police should wait until they have clear evidence, or the investigation will just go the way the government wants it to," he said.

However, PM's Secretary-General Prommin Lertsuridej insisted there had not been a set-up. He said the officer arrested was from a group the government had been watching closely.