Assistant national police chief Lieutenant-General Thawatchai Pailee said the four men had turned out to be businessmen.

Suspected bomb-making components seized by police were actually fuses and electrical equipment used in the mining industry.

"After a thorough investigation we found they are not terrorists," he said. "They have no record linking them to terrorist groups."

He said, however, the men, who were arrested in a Bangkok suburb on Tuesday night, would be deported for overstaying their visas.

BBC Sports Correspondent Harry Peart said the arrests underline how nervous the security forces are during the countdown to the Asian Games starting on Sunday.

The games are being billed as the last major sports festival of the millenium. With more than 40 countries taking part, representing more than half the world's population, Thailand has mounted its biggest peace-time security operation.

Police have detained hundreds of illegal immigrants, many of them from Cambodia, as part of searches for suspected terrorists.

Accusations

But the arrests sparked angry accusations from the Pakistan embassy, with Ambassador Sher Afgan Khan alleging one of the detained men was badly beaten when he refused to sign a confession - a claim police emphatically denied.

The other three men signed confessions under duress, the ambassador said.

"We are against terrorism, but innocent people should not be arrested just to put feathers or achievement in your cap," he said.

Four suspected Pakistani terrorists were released in June after being held by Thai authorities after they were linked to the 1993 World Trade Centre bombing in New York.