However, police found all the calls were hoaxes and no real bombs were found at any of the sites.

The nine sites included two schools and The Nation Building. These three places received bomb threat calls.

The two schools were Sanphawut Wittaya School and King Phet School.

The police emergency call centre - the Chao Fah Centre or 191 hotline - received phone calls from residents near the other six sites reporting suspicious materials in the area and asked police to check them out.

The two schools decided to temporarily close after receiving the calls. They then waited for a police inspection.

Like the two schools, the manager of The Nation Building decided to ask most companies in the building to stop working and temporarily close, letting workers go home early. The call was received at around 1pm.

"The mysterious caller claimed he was working for Thaksin and had set the bomb to go off at 1pm in our school. He then terminated the call. We received three such calls," Methinee Narknongharn, an operator at King Phet School told police.

An operator at The Nation Building said: "He [the caller] said 'listen carefully. I have set three bombs in your building that will go off in three hours. I don't mean to hurt anyone but to react to your news reporting that attacks Thaksin unfairly'."

Police sent teams to inspect the six sites for suspicious materials. The first was at 8am at Oishi Restaurant on Phaholyothin Road. The police later found the suspected box contained ceramic plates.

At noon, a similar call happened in central Bangkok on Charoenkrung Road at a beauty salon. There, police found only an empty sack.

An hour later at a noodle shop near the Air Force base on Vipawadi Road, police found another sack containing only cloth. At Central World Plaza and Gaysorn at 4pm, police found a backpack but no bomb. Two hours later it was a a similar story at two bank offices on Phaholyothin Road.

Bomb threats were also made to two schools in Nonthaburi, leading to their closure yesterday, but again the police found no bomb.

In Phitsanulok, four major shopping centres as well as the Phuthachinarat Hospital were threatened. In Kanchanaburi, there was a call to the central bus station. Hoax calls were also made to Satun's La Ngoo Hospital, Roi Et's provincial hospital and Chiang Mai's Tesco Lotus Super Centre.

A spokesman for the Metropolitan Police, Pol General Phinit Maneerat, revealed yesterday that there were a total of 119 calls from residents of Bangkok to the 191 emergency call since December 31 and 23 of them were related to bomb threats. The rest of them reported suspicious materials or packages left in public places.

"It is good to have more eyes to help us in our work. However, I would like to ask the public not to panic. For those who made threatening calls for fun, they could be jailed for as long as 18 months," he said.