The White House has said a raid in Yemen on an al-Qaeda stronghold that likely killed civilians was a “very thought-out process”.
As many as 23 civilians were killed in the raid on a village in Yakla district on Saturday, including 10 children, rights group Reprieve says.
Yemeni reports say the victims included the daughter of Anwar al-Awlaki, a militant killed by a US strike in 2011.
The raid was the first such operation authorised by President Donald Trump.
The US military had previously said a Navy Seal, William ‘Ryan’ Owens, 36, died and three others were injured. But the US Central Command (Centcom) later said that those killed could include children.
Several Apache helicopters were reported to have taken part in the operation, which killed 14 militants, including three al-Qaeda leaders, according to the US military.
White House spokesman Sean Spicer told journalists: “It’s hard to ever call something a complete success when you have a loss of life or people injured.”
“But I think when you look at the totality of what was gained to prevent the future loss of life… I think it’s a successful operation in all standards.”
He made no mention of civilian victims.
Earlier on Thursday, Reprieve said a newborn baby was among 10 children killed in the attack.
It also cited local reports as saying that a heavily pregnant woman was shot in the stomach during the raid and subsequently gave birth to an injured baby boy who later died.
Images of several dead children emerged on social media soon after the attack took place.
Earlier this week, Pentagon spokesman Capt Jeff Davis told reporters to “take reports of female casualties with a grain of salt”, adding that they had been “trained to be ready and trained to be combatants”.
But US military Central Command on Wednesday acknowledged that a number of civilians had been “likely killed in the midst of a firefight”.
Mr Trump travelled to Dover Air Force Base in Delaware on Thursday to receive the body of the US Navy Seal, William ‘Ryan’ Owens, who was killed in the raid.
Al-Qaeda has taken advantage of the civil war in Yemen to entrench its presence in the south and south-east of the country.
For the past two years, Yemen has been embroiled in fighting between forces loyal to the internationally recognised president, backed by a Saudi-led coalition, and Shia Houthi rebels.