BANGKOK, July 24 (Xinhua) -- Four people were killed in a suspected Muslim rebel attack on a military base in southern Thailand's Pattani province, authorities said Wednesday.

Among the dead in the late-night attack were an army sergeant-major, two defence volunteers and a villager, according to Colonel Thanawee Suwannarat.

The insurgents struck the remote base with grenades and automatic fire, stole machine guns, burnt tyres and scattered spikes on the road as they fled the scene, he added.

Two others remained in critical condition in the hospital, confirmed a local police officer.

The attack, one of the deadliest single incidents to hit Thailand's conflict-ridden "Deep South" in months, came as anger mounted over the case of Abdulloh Esormusor, a Muslim rebel suspect who was left critically ill and unconscious after being arrested under martial law and was subject to hours of interrogation by the military over the weekend.

Pattani has been haunted by violent attacks by separatists since 2004. More than 9,900 violent incidents have been recorded to date, including bombings, ambushes and arson attacks with more than half of the slain victims being civilians, said reports.