Police and the ruling Thai Rak Thai Party have dismissed such suspicions and insisted the alleged assassination plot was real.

Thaksin said on Friday he had been informed that four retired and active military officers were behind the alleged bomb plot targeting him. However, he rejected speculation that his mentor-turned-critic, MajGeneral Chamlong Srimuang, was involved.

Abhisit Sunday called for urgent action against the alleged masterminds.

"The prime minister said with confidence that four military officers were behind a plot to assassinate him. If he knows who they are, the government must arrest them straightaway or the attempted assassination will remain a controversial issue with the public," Abhisit said at the Democrat Party headquarters.

He also urged the government to be more cautious in its remarks and avoid exaggerating an issue that could affect the country's image.

Abhisit said Thai society had already been divided and the matter should not be played up for political gain.

He urged the relevant authorities to uncover the facts of the matter and not jump to the conclusion that last week's incident was an attempt on Thaksin's life.

Abhisit noted that when Thaksin first came to power in 2001, he had made a similar claim [about a plot to kill him] after a plane he was due to board mysteriously burst into flames on the tarmac at Don Muang Airport. An official investigation later found the explosion was an accident.

Democrat spokesman Ongart Klampaiboon Sunday said police were too quick to conclude the discovery of the carload of explosives was an attempt to kill Thaksin. He said questions had been raised in many quarters that the incident was pre-organised and this suspicion was fuelled by the lack of public trust in Thaksin and his administration.

The Nation