Five policemen were killed and another was critically wounded on Wednesday in a roadside bomb attack in Thailand\'s restive south, police said. Insurgents detonated a bomb hidden by a bridge in the Raman district of Yala province as six policemen travelled on the road in a pickup truck. The blast overturned the truck, sending it plunging into a canal and killing four of the policemen immediately. Another died on the way to hospital while a sixth was in a critical condition there. After the attack an unknown number of insurgents seized a dozen firearms including pistols and machine guns. The police had been deployed to protect teachers who have been frequent targets of militants. A shadowy insurgency, without clearly stated aims, has raged in Thailand\'s three southernmost provinces — Pattani, Narathiwat and Yala — since 2004. Daily bomb or gun attacks have targeted soldiers and civilians, Buddhists and Muslims, claiming more than 5,000 lives in eight years. A state of emergency is in force in the worst-affected parts of the region which rights campaigners say gives tens of thousands of military troops based there legal immunity, fuelling rights abuses.