A bomb attack on US troops north of Kabul Tuesday killed three soldiers and three Afghan civilians, military and Afghan officials told a foreign news agency. The attack was carried out near Bagram, a town about 50 kilometres (30 miles) north of Kabul where the United States has its largest military base in Afghanistan, officials said. "Three International Security Assistance Force (ISAF) service members were killed and one injured after an improvised explosive device attack in eastern Afghanistan this morning," ISAF said in a statement. The US military and another ISAF official said separately that the bomb had hit US troops. The ISAF official had said his first information was that four US soldiers had died. The military could not confirm Afghan reports that it was a suicide attack. Afghan interior ministry spokesman Zemarai Bashary told AFP: "A suicide car bombing has happened and the target was an international forces convoy. "The initial report we have received says three civilians were killed and three wounded." The civilians were just passers-by and it was not yet clear who they were, he said.