The insurgent attacks were the first since the death of King Bhumibol Adulyadej last month, and defied a request by the military junta to desist while the nation mourns a much-loved monarch who had reigned for seven decades.

Three people were killed, including two security guards and a soldier, according to Pramote Prom-in, a spokesman for the military's Internal Security Operations Command.

The latest attacks took place in Narathiwat and Pattani province, two of three Muslim-majority provinces in predominantly Buddhist Thailand where a separatist insurgency has been raging since 2004, and in neighbouring Songkhla province.

"It was the work of insurgents who want to create unrest and destroy trust in the government," Pramote told Reuters.

No group has so far claimed responsibility.

The overnight attacks were the biggest since a series of bomb blasts across Thailand's south in August which killed four people and injured dozens, including foreigners.

Talks aimed at bringing peace to the troubled south between the military government and an umbrella insurgent group in September failed to reach any breakthrough.

Over 6,500 people have been killed in Thailand's southernmost provinces of Yala, Pattani, and Narathiwat over the past 12 years as part of the insurgency.

"This attack shows that the insurgency situation in the south is isolated from what goes on in the rest of Thailand," Srisompop Jitpiromsri, director of Deep South Watch, a group which monitors the conflict, told Reuters.

"Any request by the junta for a halt in the violence is unlikely to have any effect."