Saudi security forces have killed seven insurgents in an ongoing siege in the northern town of al-Ras, according to security sources. Aljazeera said clashes were still going on as insurgents hurled grenades at police from their hideout in al-Ras in the al-Qassim region, 350km northwest of the Saudi capital Riyadh. A ministry statement said an eighth militant was critically wounded and a number of members of the security forces were injured, though most had been released from hospital. Security sources earlier said eight militants were killed. "Security forces are continuing mop-up operations at the site," it said about one of the longest and bloodiest battles in Saudi Arabia's two-year confrontation with al Qaeda supporters. Witnesses said gunfire could still be heard on Monday morning in the neighbourhood of al-Ras which security forces had surrounded since early Sunday. Officials described the insurgents as "terrorists". Aljazeera has learned that at least one Saudi police officer was shot dead on Sunday and another 15 had been wounded by midday. Other sources said a total of 35 security personnel had been wounded.