A severely wounded woman was taken straight into surgery and the Muslim driver, the only other person on the minibus, escaped with minor wounds, Acra said.

'Red zone'

The minibus was headed for Hat Yai, the commercial capital of the predominantly Muslim south, from Betong on the Malaysian border.

"The militants, probably newly-trained youths, picked the van as the target because those people couldn't fight back and they could avoid sustaining casualties"

Colonel Acra Tiproch, army spokesman
The attack on Wednesday, in an area classified as a "red zone" where support for the separatists is strong and security forces have previously been ambushed, may have been carried out by inexperienced fighters, Acra said.

"The militants, probably newly trained youths, picked the van as the target because those people couldn't fight back and they could avoid sustaining casualties," he said.

A bomb left at the scene was typical of the separatists' methods, aimed at inflicting casualties on security forces arriving to investigate an attack, Acra said.

The separatists usually target security forces or individuals suspected of dealing with the government and never claim responsibility for their attacks.

The shooting took place on the anniversary of the founding of the separatist Barisan Revolusi Nasional (BRN), or National Revolutionary Front, which the government had feared would be marked by an increase in violence.

Travel warnings

Australia has issued two travel alerts for Thailand in the past few weeks, saying intelligence pointed to a high threat of bombs attacks and security forces are on full alert in the capital, Bangkok.

Already this week, a Myanmar migrant worker has been beheaded, several schools - often targeted as a symbol of the Bangkok government - have been burned down and a bomb was set off at a morning market.

A string of co-ordinated blasts across Yala, Narathiwat and Pattani provinces last month killed nine people and injured 44.

The south was an independent sultanate until it was annexed by overwhelmingly Buddhist Thailand a century ago.

More than 2,000 people have been killed in the region since the latest separatist violence started in January 2004.