Seventeen civilians have been beheaded in Afghanistan, local officials say, with 10 Afghan soldiers killed in a separate incident. The civilians died in Musa Qala district, in the southern province of Helmand on Sunday night. The 10 soldiers were killed in the same province when insurgents attacked a security checkpoint also on Sunday. Meanwhile, an Afghan soldier reportedly killed two foreign soldiers on Monday in eastern Laghman province. "Last night 17 local villagers, two women and 15 men, were beheaded by unknown people in Kajaki district," Daud Ahmadi, a spokesman for Helmand province, told Agence-France Presse (AFP) news agency. "We don't know who was behind the killings at this time. We're investigating," he added. 'Insider plot' The attack on the 10 soldiers took place in Washir district. It left four other Afghan soldiers injured and at least another five missing, reports said. It is not clear whether they were abducted or went with the attackers voluntarily. "There was an attack on one of our posts in Washir district. Ten soldiers are dead in that attack," Col Mohammad Ismaiel Hotak, deputy head of the regional co-ordinating body for the Afghan army and the US-led Nato force, was quoted by AFP as saying. But Daud Ahmadi told AFP that the attack was an "insider plot". "Five others have gone with the Taliban with their guns," he said. Both officials said that the incident was being investigated. Attacker killed The incident in Langhman province is one of at least 12 so-called "green on blue" attacks by Afghan security personnel on international troops this month. The nationality of the soldiers who were killed is not yet known. "Isaf [International Security Assistance Force] soldiers returned fire and killed the attacker," an ISAF spokesman told AFP. A total of 42 Isaf personnel have been killed by members of the Afghan security forces this year. Currently, approximately 130,000 ("blue") Nato troops are fighting insurgents in Afghanistan alongside 350,000 ("green") Afghans.