Insurgents allegedly raided a power plant where they set off bombs in Thailand's deep south.

Around 20 suspected terrorists invaded the Pracharat Biomass Mae Lan Co Ltd plant under cover of darkness, holding seven workers and two security officers at gunpoint as they detonated explosives in the facility in Pattani province on April 26.

CCTV footage shows the masked men appearing to plant improvised explosives fashioned out of fuel cylinders at different points of the plant.

After detonating the bombs and setting fire to the factory, they reportedly left without harming the employees.

Police Captain Natee Meesuksri of the Mae Lan Police Station said the explosions had damaged a water treatment building, a control room, an air compressor, a turbine installation, a wood chips warehouse, and several workers' vehicles.

Police said the attack is estimated to have caused 27 million THB (584,000 GBP) in damages. They said an insider may have been involved as the blasts appeared to have targeted specific parts of the plant.

Police Colonel Somyot Sombatmak, superintendent of the Mae Lan Police Station, said: 'We are investigating if the suspects might involve someone affiliated with the plant. They knew where the equipment was located.'

Ten of the attackers were reported to have come from the forested area behind the factory, while another ten entered from the front.

Employees said they were brandishing firearms and shouted 'We will plant 10 bombs in the factory'.

The men reportedly kicked the workers out of the building before setting off the explosives.

Jemaah, the factory's security chief, said: 'I didn't see what they looked like because they were wearing masks. I was too scared to look closely.

'They planted bombs at a generator and other important spots of the factory as if they knew where they should target. Prior to this attack, there were no strange incidents here.'

One of the workers, Arun Pongkongjan, said: 'I was working before the armed men suddenly invaded and told everyone to lie on the ground. I did not know what they were going to do.

'I saw three of them wearing masks and touting guns.

'They told me and my colleagues to go downstairs and get out of the factory quickly without hurting me. After we escaped, the explosions started.'

The factory is a ready-to-burn biomass power plant under the Very Small Power Producer (VSPP) project, which will utilise leftover biomass items in the area such as fuel, chopped rubber roots and other leftover agricultural materials.

Following the blasts, an Explosive Ordnance Disposal team searched for remaining bombs at the factory.

A 15kg explosive device made up of a fuel cylinder was still in the premises and is yet to be detonated as its timer was still running, local media reported.

Islamic separatist terror attacks target the three southernmost provinces of Thailand - Yala, Pattani and Narathiwat - next to the border with Mulsim neighbors Malaysia. Thai state employees and infrastructure are often hit while attacks on civilians are rare.

Officials believe the conflict dates to a deal in 1909 that the British Empire struck to incorporate the Muslim region into the Siamese mainland.

The region's culture is more similar to Malaysia and dramatically different to Buddhist Thais causing decades of tension that lead to the emergence of separatist groups fighting for independence in the 1960s.

The struggle has continued ever since with more than 7,344 people killed and 13,641 injured between January 2004 and March 2022.

The British Foreign & Commonwealth Office warns against all but essential travel to the region while Canada's government warns its nationals to 'avoid all travel' to the three provinces.