The blast follows a series of blasts in the region on Saturday

The blast in Sukhirin, in the mainly Muslim province of Narathiwat, comes a day before a scheduled visit by Prime Minister Thaksin Shinawatra.

Soldiers, police officers and schoolchildren were among the injured.

A spate of attacks blamed on Muslim separatists has killed more than 300 people since January.

Attackers have targeted symbols of the mainly Buddhist Thai state such as official buildings and the security forces.

The bomb went off at a market where members of the security forces often go to eat breakfast, police official Lt Col Amnuay Pongsawat told AP news agency.

Thailand's Muslim divide

It is thought that the bomb was triggered by remote control when a lorry carrying security officials pulled up.

Prime Minister Thaksin said he would not let the latest attack put him off visiting Narathiwat on Friday.

"There have been other bomb blasts even before my trip. Don't blow it out of proportion," he told reporters in the southern city of Krabi.

He said the latest attacks were a response to increased pressure from the country's security forces.

"We now know their network and are able to arrest more of their cells, so they are resorting to more violent attacks to boast about their capacity and we have to be more vigilant," he added.

Southern Thailand has been the victim of several attacks and attempted attacks in the last few days.