The top military brass and the police spokesman yesterday dismissed reports of a plot to kill the prime minister as virtually groundless. But the news succeeded in raising the political temperature across the Kingdom to a feverish height.

"We have not found any evidence of an assassination attempt against Police Lt-Colonel Thaksin [Shinawatra]. Still, we need to take precautions. We have to step up our intelligence [monitoring]," Supreme Commander General Ruengroj Mahasaranond said.

Asked whether news of an alleged assassination plot could hurt national security, Ruengroj said: "It's natural that these kind of stories can appear. But they are mostly rumours."

Thaksin has beefed up security around him in recent days following rumours that an attempt would be made on his life.

He stirred up the already overheated political mood when he said the National Intelligence Agency chief had warned him about the alleged plot.

The rumours come at a time of growing political pressure on him to identify the "person with reserved power" he said was trying to overthrow his government by unconstitutional means.

Adding more controversy were Thaksin's letters to US President George Bush and Asian leaders. The caretaker premier has been accused of seeking support from his international counterparts for his political predicament at the expense of sound diplomacy and Thailand's international standing.

Police spokesman Lt-General Ajiravid Subarnbhesaj said the alleged assassination plot was likely to be an attempt at disinformation. He called on the media not to alarm people with unconfirmed reports as it could harm national security.

Ajiravid said the Special Branch and the Royal Thai Police's Information Operation Centre have not heard or uncovered any assassination plot and he had been checking every three to six hours.

"This report might be a joke that has spread unintentionally," he said. If there was an assassination plot, the news could not have spread out like this, he said.

Meanwhile, Thaksin further said he was not especially worried about his own security as the number of his bodyguards had been increased "a little bit".

When asked whether he thought the "threat" on his life was real, Thaksin said the matter was still under investigation.

Ruengroj called on the Thai people to follow His Majesty the King's advice to preserve unity, and not to believe propaganda easily.

"Thais should not be divided. All Thais are subjects under His Majesty the King. We all love the King and we all are Thai people," the supreme commander said.

"Conflicts are dangerous to the country so Thais should face each other to talk it out. We have lessons in our history that bad events usually follow conflicts. However, I can assure the military is firm with its neutral position," he said.

Air Chief Marshall Chalit Pukpasuk said the Royal Thai Air Force has also been trying to promote national unity and that judicial attempts to break the political deadlock were the best way out for Thailand.