KABUL (AFP) - A police officer and six militants have been killed in military operations in southern Afghanistan, the US-led and Afghan forces said Saturday. The police officer died in a gun battle Friday set off when the two forces raided a manufacturing and storage facility for explosives in the southern province of Helmand, the coalition said. "The combined forces responded with small-arms fire and heavy weapons, killing one militant... During the engagements, one Afghan police officer was killed and another was wounded," it said in a statement. A combined Afghan and coalition forces patrol was ambushed by militants in the same area Thursday, sparking a gun battle, the statement said. "The combined forces returned fire... killing four militants; they also discovered six IEDs (improvised explosives devices) in the area and destroyed them," it said. The coalition forces also killed an insurgent and detained six others in neighbouring Zabul province on Friday. "During the operation, coalition forces killed one militant armed with an AK-47, grenades and other military equipment after he engaged the force," a separate coalition forces press statement said. The troops also arrested eight suspected militants in a raid 30 km outside the capital Kabul, coalition troops said. Meanwhile, four British troops were killed in two separate explosions Friday in Afghanistan, the Ministry of Defence said. "Four Royal Marines were killed in two separate incidents in the Sangin area of Helmand province this morning," the MoD said in a statement. In the explosion which occurred south of the town of Sangin, three marines - two from 45 Commando and one from Commando Logistics Regiment - were killed. "They were taking part in a routine operation against enemy forces in the area," the MoD said. The other explosion took place in the Sangin area. One soldier from 45 Commando, who was taking part in a routine patrol, was killed as a result. He died of his wounds while being taken to Camp Bastion.