At least seven members of Afghan National Police have been shot dead by their colleagues at a police outpost in the troubled southern Afghanistan.Afghan security officials say two policemen shot dead seven of their sleeping colleagues in the Arghistan district of the southern province of Kandahar on Monday night. "As soon as the policemen fell asleep, the pair grabbed weapons and opened fire, killing all seven," Kandahar Afghan National Police chief Abdul Raziq said. The attackers managed to flee the scene after the deadly shooting spree. The incident is the latest in a series of Afghan security personnel targeting their local and foreign colleagues across the war-ravaged country. Over the past months, there has been a rise in the ‘green-on-blue’ attacks in Afghanistan, in which Afghan security forces turn their weapons on US-led foreign troopers. In addition to that, Taliban militants recently announced the start of their annual "spring offensive" against US-led and Afghan forces, vowing a new wave of attacks across Afghanistan. The United States and its allies invaded Afghanistan in 2001 as part of Washington’s so-called war on terror. The offensive removed the Taliban from power, but insecurity remains across the country despite the presence of thousands of foreign troops.