The wave of violence did not spare schools

Most of the injured - in Sungai Kolok, a town on the border with Malaysia - are said to be Thais and Malaysian tourists.

The motorcycle bomb exploded around 1930 (1230 GMT) near a karaoke bar popular with Malaysian tourists.

The area has been under martial law since an armed raid in January on an army camp sparked violence that left more than 50 people dead.

This is one of the most serious incidents, says the BBC's Kylie Morris - and a reminder that the problem has not been solved, despite a government reshuffle and the sacking of security officials.

Expected?

No one has admitted planting the device, on a motorbike parked outside the "Top Ten 2004" karaoke bar.

"This is part of the ongoing unrest," police captain Paibul Wattatham said.

Thailand's National Intelligence Agency chief Lt Gen Chumpol Manmai had warned of a possible major attack after the arrest this week of several people alleged to have been behind the January raid on an army depot, which killed four soldiers.

"We expect the violence to continue for some time," he said.

An arrest warrant has been issued for a governing party member of parliament, Najamudeen Umar, on suspicion of involvement in the raid.

Martial law still applies across the Muslim majority provinces in the country's south.

The government says it plans to install closed circuit television in state buildings and other sensitive areas to halt the escalation in what it called urban terrorism.