KUALA LUMPUR, - Political trouble-makers and not Muslim rebels are likely to have been behind a small bomb that exploded near the royal palace in Bangkok, Deputy Foreign Minister Sawanit Kongsiri said on May 7.

Speaking on a visit to Malaysia, Sawanit said Saturday's blast, which wounded one person slightly, appeared to have been designed to create tensions ahead of elections due in December.

"We doubt it," he told reporters when asked if he suspected rebels from the Muslim-majority far south had been behind the blast.

"We have had it before, in isolated bombing incidents placed in areas that will cause a little bit of panic but no deaths -- to raise the political tensions."

Thai security forces tightened security in the capital after the blast, which followed a series of New Year's Eve bombs in Bangkok that killed three people and wounded 38.

Until the Bangkok bombings, unrest appeared to have been restricted to the country's far south where Muslim separatists have waged a three-year insurgency in which more than 2,100 people have been killed.

On Monday, unknown gunmen shot dead two Thai buddhists, a man and his 20-year-old daughter, in an ambush in the region, police said. Such attacks happen almost daily.

Sawanit, whose government was appointed by the military after it seized power in a coup last September, drew a distinction between the violence in the south and the smaller-scale attacks in the capital.

There was talk the culprits in the latest Bangkok bombing could be supporters of two Thai political parties, the Thai Rak Thai (Thais Love Thais) party of ousted former Prime Minister Thaksin Shinawatra and the Democrat party, he said.

There was similar talk after the New Year's Eve bombs, for which no arrests have been made, but police later said the bombs were of the same kind used in the far south.

Both Thai Rak Thai and the Democrat party face allegations of electoral fraud. A court is expected to hand down its decision on the case by the end of this month, Sawanit said.

"If they are proven guilty, they will have to dissolve their political parties," he said.

"So there is a belief in some circles that people are creating these tensions in order to try and upset the court decision," he said.

The motive might be get the cases "postponed and that will help them,", he added.

However, the government was determined to go ahead with the elections promised for September and was quietly stepping up security in Bangkok.

"We recognise that there is instability at the moment. We are in the run-up to elections and this very important court case being decided," he said.