Three people including two policemen were killed and 21 people were injured in a series of bomb blasts and shootings across Thailand's troubled south, officials said today.

Three blasts occurred almost simultaneously late Wednesday in the town of Sungai Golok on the Malaysian border, injuring 15 including four who were seriously hurt, police said.

"An unknown number of militants put the explosive material inside plastic bags and placed them at (three locations) and triggered them with a mobile phone," Sungai Golok police said in a statement.

The bombs began exploding at 8:35 pm, the first one at a karaoke bar and then at two hotels, the Plaza and the Genting.

The wounded included a male Malaysian tourist identified only as Ah Hua, who was hit in the stomach with shrapnel, and a Laotian immigrant worker who was not named.

In Pattani province, supected Muslim separatist militants used 11 bombs rigged from fire extinguishers in an attempt to blow up two bridges in Nongchik district in Pattani province but not all the bombs exploded, police said.

"There were 11 bombs tied to pillars under the bridges but only a few of them exploded," said Pattani governor Cherdpan Na Songkhla. No one was injured in the explosions.

Cop killed

Southern army commander Lieutenant General Kwanchart Klaharn said the militants had stepped bomb attacks across the southern provinces which border Malaysia as they came under heavy pressure from authorities.

"There have been frequent bomb blasts recently because the militants want to show off their potential and prove that they still have enough forces to mount attacks," Kwanchart told reporters.

In the third bomb incident, a police officer who was escorting teachers to school was killed and his colleague and two teachers were injured in an explosion in Sungai Padi district of Narathiwat province early Thursday.

"Sergeant Thaworn Raknim died immediately from the roadside bomb as he and his police colleague, who was also injured, escorted teachers to school," police said.

Another bomb placed in a pot plant in Narathiwat provincial town exploded early Thursday, injuring three villagers.

Thai muslims detained

In other violence in the restive region, a highway police officer was shot and killed in Pattani province while manning an outpost along the Pattani-Hat Yai highway Wednesday night, police said.

And in Yala province, Muslim religious teacher Abduloh Malee, 38, was shot in the head by two gunmen as he travelled to the Islamic Pattana Wittaya school. He died instantly early Thursday.

Reports in Malaysia said police have detained some 131 Thai Muslims, including women and children, who said they were fleeing violence in the south where nearly 900 people have been killed in the past 20 months.

The official Bernama news agency said the illegal immigrants sought refuge in several mosques in northeastern Kelantan state which borders Thailand.

The New Straits Times cited police sources as saying they feared thousands more could cross over into Malaysia in the next few days.