Two bombs have exploded in southern Thailand's Pattani province, killing two policemen and injuring others.
Southern Thailand has been put under martial rule
The policemen died when a bomb they were trying to defuse, which had been placed on a motorcycle, went off.
The incident came as martial law was declared in Pattani and two other provinces following weekend raids blamed on separatists turned bandits.
Gunmen killed four soldiers during a pre-dawn raid on an army weapons depot on Sunday, stealing more than 100 guns.
Thai Prime Minister Thaksin Shinawatra said weekend arson attacks on 21 schools were designed to distract the authorities.
Home to most of Thailand's 4% Muslim minority
Muslim rebels fought the government up to the mid-80s
Government downplays any separatist threat, calling them bandits
The BBC's Kylie Morris in Bangkok says the latest attacks are a further set-back to the government, which is already defending itself against criticism that it has under-estimated the problems in the country's predominantly Muslim south.
Mr Thaksin blamed Sunday's attacks on a Muslim group called the Mujahideen, known to operate from southern Thailand and Malaysia.
He suggested they would sell the weapons to allied groups, including separatists in the Indonesian province of Aceh.
Martial law has been imposed on Pattani, Narathiwat and Yala as authorities search the Thai-Malaysian border for suspects and weapons.
Mr Thaksin blamed a lack of co-ordination between the police and the army for the weapons raid.
"The security forces, with more than 2,000 soldiers in the camp, they knew about the bandits looking for a big lot of weapons. But still they were negligent. They deserved to die," he said.
There has been sporadic violence in Thailand's 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.
Thai security officials say most of the separatists in the area are now bandits who run rackets along the Thai-Malaysian border.
An army spokesman has described the weekend violence as the worst in the past 12 months