A US air strike called in to suppress an attack in Kabul on Wednesday as Defense Secretary Jim Mattis was visiting the Afghan capital caused a number of civilian casualties, the NATO-led Resolute Support mission said.
The US strike was launched in support of Afghan security forces who had confronted militants after they fired a volley of rockets near the capital's international airport hours after Mattis arrived in the country for talks.
One person was killed and 11 others were wounded in the assault, according to the interior ministry. The Taliban and Daesh's local Khorasan province affiliate claimed responsibility.
"Tragically, one of the missiles malfunctioned, causing several casualties," NATO's Resolute Support mission said in a statement.
NATO said it "deeply regrets the harm to non-combatants" and an investigation was under way into the attack and the defective ammunition.
The casualties caused by the US air strike in the capital have cast a pall over Mattis' trip to the country and could fuel anger towards American forces whose reputation is already tarnished.
Earlier this month, US forces distributed leaflets in the northern province of Parwan that were deemed highly offensive to Muslims and sparked angry protests.
Mattis is the first member of US President Donald Trump's cabinet to visit Afghanistan since Trump last month pledged to stay the course in America's longest war.
His unannounced visit came as the country's beleaguered security forces struggle to beat back the Taliban, which has been on the offensive since US-led NATO combat troops withdrew at the end of 2014.
Mattis, along with NATO chief Jens Stoltenberg, held talks with Afghan President Ashraf Ghani to discuss the US-led NATO "train and assist" mission – designed to strengthen Afghanistan's military.