At least 25 people have been killed by an explosion outside a school south of the Afghan capital; in the bloodiest single attack in a year.The device went off early this morning as police checked a vehicle abandoned between two schools situated in Logar province. Officials say the explosives were hidden beneath a pile of firewood in the back of he truck which had crashed overnight, sparking speculation they were meant for elsewhere – possibly an attack in Kabul. The Taliban have been active for some time in the region which lies close to the militant group’s eastern strongholds. Dozens of Afghan civilians and troops have been killed in a variety of attacks this week. At least 17 foreign soldiers, including seven Britons, have also been killed in the past six days, making it one of the bloodiest weeks for allied forces in many months.