The US special forces mounted the raid in the Yakla region of Baida province against Al-Qaeda in the Arabian Peninsula (AQAP), which Washington views as the global terror network’s most dangerous branch.

A US service member was killed during a firefight and three others were injured in a hard landing of a V-22 Osprey military aircraft nearby, Davis said.

On the AQAP side, 14 fighters, including women, were killed, according to the Pentagon. The jihadist militant group said nearly 30 people were killed, including women and children.

The gunbattle killed a senior leader of AQAP, Abdulraoof al-Dhahab, along with other militants, al Qaeda said.

Eight-year-old Anwaar al-Awlaki, the daughter of US-born Yemeni preacher and al-Qaeda ideologue Anwar al-Awlaki, was among the children killed in the raid, according to her grandfather. Her father was killed in a US drone strike in 2011.

“She was hit with a bullet in her neck and suffered for two hours,” Nasser al-Awlaki said. “Why kill children? This is the new [US] administration - it’s very sad, a big crime.”

A US military official, speaking on condition of anonymity, said civilian casualties could not be ruled out.

The Pentagon declined to say whether children were among the fatalities and stated that the death toll was still being evaluated.

The operation, which US President Donald Trump said “will assist the US in preventing terrorism against its citizens and people around the world,” was the first major US military action in Yemen since he took office on January 20.

According to the Pentagon, it was aimed at gathering information, using a lightning raid by special forces to seize the maximum amount of documents, computers or other electronic devices before pulling back.

The US military notably wants to be able to improve intelligence on AQAP operations after the militants redeployed to the interior of the country after being chased from the coastal areas between Mukalla in the southeast and Aden.

“Since they were ejected out of Mukalla and have moved to the countryside, into the desert, they have been in many ways in a much more friendly environment,” Davis said.

The raid, he said, “was specifically to enable us to gather the information we needed to be able to map out this group better and to prevent future foreign terrorist attacks.”

The raid authorised by Trump was in preparation for some time and former president Barack Obama was aware of it, the spokesman said.

“There were operational reasons to why it did not happen, say, two weeks ago,” when Obama was still the commander-in-chief, he said.

Additional reporting by Associated Press