An American airstrike on insurgents in Kabul Wednesday caused "several casualties" after a missile "malfunctioned", NATO said, overshadowing a high-profile visit by US Defense Secretary Jim Mattis and NATO chief Jens Stoltenberg.
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 the Islamic State'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.
Afghanistan's president Ashraf Ghani (L) and US Defense Secretary James Mattis (R) attend a news conference in Kabul, Afghanistan on September 27, 2017.
NATO said it "deeply regrets the harm to non-combatants" and an investigation was underway into the attack and the defective ammunition.
The casualties caused by the US airstrike in the capital have cast a pall over Mattis's 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 Stoltenberg, held talks with President Ashraf Ghani to discuss the US-led NATO "train and assist" mission –
designed to strengthen Afghanistan's military so it can defend the country on its own.
At a joint news conference with Ghani at the presidential palace, Mattis and Stoltenberg renewed their commitment to Afghanistan, and expressed determination to stop the country becoming a safe haven for terrorists.
"We will not abandon Afghanistan to a merciless enemy trying to kill its way to power," Mattis told reporters in reference to the Taliban.
Stoltenberg said: "The more stable Afghanistan is, the more safe we will be."
So far, more than 15 NATO members have agreed to send additional troops.