"Police investigation into the matter has corroborated the observations of the premier's security staffs about the car. It was found appearing at many places where the premier went," the spokesman said.

Thawatchai was arrested on Thursday after police found a Daewoo car he was driving was loaded with heavy explosive devices. It is still unclear whether the explosives were assembled and ready to be detonated.

Achirawit said Lt Thawatchai insisted that he had just been hired to drive the car.

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

The licence of the vehicle was genuine, issued by Land Transportation Department. The owner of the vehicle would be summoned for questioning, the spokesman said.

Bomb experts insisted that if the explosives' circuits had been connected, it would have had an impact over a radius of around one kilometre.

The police spokesman said the assassination plot was not a hoax as the premier's motorcades would have passed the place where the suspect had parked his bombladen vehicle.

"We believe there are more than two people involved in the attempt. When we have solid evidence, we will ask for arrest warrants," the spokesman said.

At the moment, Thawatchai is charged only for being in possession of explosives without permits. "By law, preparing to commit suicide is not considered an offence."

The spokesman urged all sides to cease speculation and wait until the police investigation was complete.

The Nation