US air strikes aimed at Islamic State militants killed 20 civilians between September and February in Iraq and Syria, the US military has admitted.
US Central Command identified nine separate strikes – six in Iraq and three in Syria.
It said it deeply regretted the unintentional loss of life.
It said a total of 41 civilians had been killed since the air strikes began in 2014. Some human rights groups say the figure is much higher.
Announcing the results of several investigations, US Central Command said “the preponderance of evidence” indicated that 20 civilians were killed and 11 other wounded in the strikes between 10 September 2015 and 2 February 2016.
The heaviest casualties were in October, when eight civilians died in an attack in Atshanah in northern Iraq. The US military did not provide further details of that strike.
It also said that five civilians were killed in a strike on a suspected IS target in Ramadi last December.
The civilians “unexpectedly moved into the target locations after weapons were already in flight,” the military said.
Central Command spokesman Col Patrick Ryder said the US deeply regretted the casualties.
He added that the US operation was “the most precise air campaign in the history of warfare”.
Washington says it has carried out nearly 12,000 air strikes since it launched its operation in Iraq in August 2014 and a month later in Syria.