A bomb allegedly planted by separatist insurgents on a hijacked garbage truck injured three officers when it exploded in southern Thailand.

CCTV footage captured the green waste truck - reportedly loaded with a hefty 50-lb explosive device - being parked near a petrol station and a police checkpoint in the Panare district of Pattani province on June 20 evening.

Its occupants drove away on a motorcycle shortly before the improvised bomb was detonated remotely at 9:15 pm local time.

The blast knocked out power to the surrounding area as it destroyed electric cables, forcing the police to defer their investigations until the next morning.

Three policemen manning the checkpoint, which was within the bomb's 100-metre explosion radius, had minor injuries. Police Corporal Nattakit Chiewchan was hit by shrapnel and is recovering from non-fatal wounds at the Pattani Hospital.

Investigations found that the now-demolished garbage truck had been seized from sanitary workers, who were allegedly attacked by armed masked assailants in Mayo district some three kilometres away from the blast site. The employees were found tied up and lying face-down near a forested area. Police have taken them in for questioning.

Authorities have linked the bombing to an Islamic terror group led by a certain Abdulhadi Dahamang, who has standing arrest warrants for alleged militant activity involving the acquisition of explosives in the region in recent months.

Following the incident, Police Major General Narin Busamun, commander of the Pattani provincial police, ordered officers to cordon off the area and to be on high alert for suspicious activity. Strict checkpoints have been established to screen vehicles entering Mayo and Panare districts.

The southernmost provinces of Thailand - Yala, Pattani and Narathiwat - have been blighted by terrorism for several decades. It stems back to a deal in 1909 between the British Empire to incorporate the region into the main country of Siam.

However, the area is made up primarily of Malay Muslims with a culture more similar to Malaysia and dramatically different to Buddhist Thais. Following years of tension, armed separatist groups emerged fighting for independence in the 1960s.

The struggle has continued ever since with more than 7,290 people killed between January 2004 and October 2021. There were an average of 38.8 incidents and 36.7 casualties a month in 2021, according to data from Deep South Watch.

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.