The attack at about 9am marked the first US air strike to defend the city.
Read: US air strike kills 'Islamic State's number two': White House
"US forces conducted an air strike in Kunduz today to eliminate a threat to coalition and Afghan forces operating in the vicinity of Kunduz," said Colonel Brian Tribus, a spokesperson for the Nato-led coalition. He did not elaborate on how many coalition forces troops were in the area.
Nato officially ended its combat role in Afghanistan last year. A scaled-down coalition presence now mostly trains and advises Afghan forces, although US drones still target militant leaders and a US counter-terror force remains.
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