KABUL (AFP) - Troops killed 60 militants and seized their largest-ever drugs haul in a just-ended operation that smashed an insurgent hub in southern Afghanistan, the military said Saturday. The four-day operation was in Helmand province where a British soldier was killed in a separate incident on Friday, officials said. The operation ended overnight when air strikes destroyed 92 tonnes of drugs and masses more heroin-processing chemicals and bomb-making materials collected in the sweep of Marja, southwest of the provincial capital Lashkar Gah. A total of 60 militants were eliminated as they mounted an ineffective and uncoordinated defence against friendly forces, a joint US and Afghan military statement said, issuing a final tally. The statement said the troops had also seized the single-largest drug cache by Afghan-led forces in Afghanistan to date. They moved all friendly elements from a bazaar in the area at midnight Friday, it said. With the area cordoned off, precision air strikes destroyed the narcotics, bomb-making materials, weapons and munitions discovered during the operation, it said. The air strikes targeted specific militant buildings used as command nodes and drug-making facilities in which attacks against Afghan and coalition forces were coordinated. Helmand, where thousands of British troops are based for a NATO-led military force helping Afghanistan, is the main producer of Afghan opium, which accounts for more than 90 percent of the worlds supply. The operation had confirmed that Marja was a hub of multiple types of militant and criminal activity, the statement said. The haul included 92,271kg of narcotics, including 75,000kg of opium poppy seeds, 16,850kg of black tar opium as well as morphine, heroin and hashish. The troops also seized an unprecedented amount of heroin-processing materials, including tonnes of chemicals and soda ash. They also discovered large amounts of bomb-making materials, including 27 tonnes of ammonium nitrate, pressure plate triggers, explosives and various types of mortars, the statement said. The four-day operation severely disrupted one of the key militant and criminal operations and narcotics hubs in southern Afghanistan, US military spokesman Colonel Greg Julian said. In other insurgency-linked incidents reported Saturday, the British defence ministry said one of its soldiers was killed in Helmands Sangin district when he was shot while on foot patrol Friday. The Afghan army said 20 more militants were killed late Friday in an ongoing operation in the northwestern province of Badghis, which borders Turkmenistan.