About 30 gunmen raided an army depot in Narathiwat province early on Sunday, stealing some 100 rifles.

It is unclear who is responsible but previous attacks have been blamed on former separatists turned bandits.

Prime Minister Thaksin Shinawatra cut short his holiday to hold an emergency meeting of security officials.

Mr Shinawatra ordered tighter co-operation between army and police units hunting down the gunmen.

Mosquito coils

The attacks appeared to have been co-ordinated between a number of different groups who moved on the same night against targets in nine districts near Thailand's border with Malaysia, an army spokesman said.

The target seems to have been weapons and ammunition stored at the army depot, the BBC's Kylie Morris in Thailand reports.

Most schools were set on fire by mosquito coils put on petrol-soaked sacks, a local radio station reported. Some of the fires were raging several hours after the attacks.

Fire engines were reportedly prevented from getting near to the burning schools by nails placed on approach roads.

No injuries were reported in the school burnings.

There has been sporadic violence in the five southernmost provinces - Songkhla, Satun, Yala, Narathiwat and Pattani - which has been attributed to Muslim separatists.

But analysts say the violence has recently eased after relatively successful government policies aimed at integrating Thai Muslims into the country's predominantly Buddhist society.