The blast occurred at 9.30 am (0230 GMT) in Yala, one of three provinces near the Malaysian border that have been under emergency rule since 2005.

"There was a bomb hidden in a fire extinguisher in a pick-up truck parked in front of a grocery shop near Siam City Bank," a local police officer said. "It caused a fire in a nearby shop and injured about eight people."

Shadowy Islamic insurgents have waged a violent campaign in Thailand's southernmost region since early 2004, leaving more than 4,400 people dead, including both Muslims and Buddhists, in near-daily attacks.

Violence appears to have intensified recently: a bomb attack in Yala province killed nine villagers last month and an unusually bold attack by militants a week earlier on a military base left at least four soldiers dead.

On Thursday three people, including a teacher, were shot dead and their bodies burned in neighbouring Pattani province, in one of a series of gun attacks in the region last week.