KABUL (AFP) - A bomb attack on US troops north of the Afghan capital Tuesday killed three soldiers and three Afghan civilians, officials said, as 13 militants were reported killed in air strikes. In other violence linked to Taliban-led insurgency, two Afghan policemen were killed in a separate bomb blast and Nato-led soldiers shot dead a civilian they believed to be a threat, officials said. The US soldiers were hit in a bomb blast near Bagram, a town about 50km north of Kabul, where the US has its largest military base in Afghanistan. Three 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. They could not confirm Afghan statements that it was a suicide attack. The Afghan Interior Ministry said three civilians were killed and two wounded, all of them passers-by, in the incident in Kapisa province about 10km northeast of Bagram. Before Tuesdays bombing, 110 international soldiers had lost their lives in Afghanistan this year, according to a toll maintained by icasualties.org. Most were killed in insurgent bomb attacks and in southern Afghanistan, a Taliban stronghold which sees the worst of the insurgency. The Pakistan-based Afghan Islamic Press news agency reported that the Hezb-e-Islami faction of former prime minister Gulbuddin Hekmatyar had said it had carried out the attack on the troops. A Taliban spokesman told AFP it was not the work of his group and pointed to Hezb-e-Islami, which is active in the area in Kapisa where mainly US and French troops are deployed for ISAF. In the eastern town of Khost, meanwhile, troops killed a civilian whom they believed to be a threat, Isaf said. It did not give details, saying the incident was being investigated. In another attack Tuesday, a bomb blew up a police vehicle in the southern province of Kandahar and killed two policemen, the Interior Ministry said. The US military said separately that coalition and Afghan forces had killed 13 militants Tuesday in airstrikes in Logar province, which adjoins Kabul.