A car bomb has exploded outside a busy supermarket in southern Thailand, injuring 60 people and ripping the building apart.

The bomb was hidden inside a pick-up truck, parked outside the Big C shopping centre in Pattani — a major grocery and retail chain in Thailand.

The attackers had earlier set off a small bomb outside the centre, causing people to gather before the second explosion.

About 60 people were injured and 20 serious cases hospitalised.

Footage of the scene aired on Thai television stations showed a huge black plume of smoke rising skyward from the blackened building as rescue workers doused the flames and soldiers stood by.

Rescue workers patrolled the scene after the blast. ( Reuters: Surapan Boonthanom )

No deaths were reported.

While attacks happen most weeks in southern Thailand, this one was significant for its size and audacity.

The likely culprits are Muslim insurgents, fighting to separate the deep south from the rest of Buddhist Thailand.

They rarely claim responsibility for attacks and the main fighting factions have rejected peace talks with Thailand's military government.

More than 6,500 people have been killed since 2004.

The awning outside the Pattani supermarket was destroyed. ( Reuters: Surapan Boonthanom )

ABC/AP