An air strike by the United States in Kabul on Wednesday, targeted at insurgents, caused civilian casualties as one of the missiles malfunctioned, said the North Atlantic Treaty Organisation-led mission in Afghanistan.

“Tragically, one of the missiles malfunctioned, causing several casualties,” its statement said. However, the number of deaths or injuries is not clear yet.

The US strike was in support of Afghan troops responding to rocket attacks by militants at the Kabul airport on Wednesday, shortly after US Defence Secretary James Mattis arrived in the city. At least one civilian was killed and four were injured after multiple rockets attacked the Hamid Karzai International Airport in Afghanistan’s capital Kabul on Wednesday. The Taliban claimed responsibility for the attack, and said that its target was Mattis.

An investigation into the attack and the subsequent malfunctioning of the missile is under way, said the Resolute Support Mission.

At least one civilian was killed and four others were injured in Wednesday’s attack at the Hamid Karzai International Airport. The Taliban claimed that Mattis was their target. The rockets had landed shortly after Mattis and the chief of North Atlantic Treaty Organisation Jens Stoltenberg arrived in Kabul. Later in the day, three explosions were reported near the airport.