A Taliban car bomber struck a NATO military convoy in Kabul on Saturday, killing 17 people, including 13 U.S. troops, in the deadliest attack to hit Afghanistan in months.

The attacker blew up his Toyota Sedan car next to a U.S.-run bus travelling through the southwest of the city at 11:20 a.m. (0650 GMT), the latest in a spate of successful high-profile attacks by the insurgents in the heart of the capital.

The Interior Ministry said three bystanders and a policeman were killed, while NATO's alliance force said at least 13 Western military forces died and U.S. officials confirmed they were all American.

“Initial reports indicate that 13 International Security Assistance Force [ISAF] service members died following an improvised explosive device attack in Kabul earlier today,” said the force in a statement.

Thick black smoke could be seen rising from a fire still raging at the scene, cordoned off by Afghan and ISAF soldiers, while fire hoses were putting out another blaze nearby, footage on private television channel Tolo showed. It was the deadliest incident in the more than 10-year war since the Taliban apparently shot down a U.S. helicopter in August, killing 30 American troops.

That attack marked the biggest single loss of life for American and NATO forces since the U.S.-led invasion of Afghanistan toppled the Taliban in late 2001, shortly after the September 11 attacks in the United States.

The Taliban claimed responsibility for the attack.

At around the same time in the eastern city of Asadabad in Kunar province, a female suicide bomber blew herself up outside a local branch of Afghanistan's spy agency, a spokesman for the Kunar provincial governor said.

The woman struck outside the local operations centre for the National Directorate of Security (NDS), said the spokesman.

The attacks come a day after the Taliban launched a four-hour long assault on a U.S.-run civilian-military base and NDS local branch in the southern city of Kandahar, the spiritual birthplace of the insurgent movement.

Also on Saturday, three NATO troops were killed when a man dressed in an Afghan Army uniform turned his gun on them, the coalition said, adding that the shooter was later killed.

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