A defence official said the slain service member was killed in a firefight with militants. According to a statement from US Central Command (Centcom), 14 militants were killed during the operation.
The raid, which took place in a remote desert area of Yemen's Shabwa governorate, aimed to obtain intelligence information, including computer material, that was thought to be linked to planning for external attacks. The official could not confirm whether US allies had participated in the raid. In recent months, US Special Operations forces have partnered with troops from the United Arab Emirates to help target and go after al-Qaeda militants in Yemen.
The assault, a Yemeni official said, killed 35 to 40 people in the village, though other figures in local media suggested a lower death toll. US troops, the official said, descended from helicopters, as militants had gathered for a late-night session of chewing qat, the leafy narcotic used by most Yemeni males, especially at social and tribal gatherings. A lengthy battle followed, as the militants opened fire on the US soldiers. Many homes were destroyed, said the official.
"The raid was intense, and wiped out most areas of the village," said the security official. "It took place from night until dawn."
Among those killed was an AQAP leader named Abdulra'oof Aldahab and two of his relatives. In total, 13 militants were killed, said the official. The operation also killed 15 women and children, said the official, including the 8-year-old daughter of the late radical-Yemeni-American cleric, Anwar Al-Awlaki who was killed in 2011 in a US drone strike.
US officials, after indicating that they could not confirm reports of civilian casualties, said they were now assessing the claims. US helicopter gunships and fighter aircraft provided cover for the raid force, according to another defence official. The aircraft dropped an unknown amount of munitions in support of the operation.
According to a report from the Site Intelligence Group, Al-Qaeda in the Arabian Peninsula reported in a message on the Telegram messaging app that US forces launched a helicopter attack and a ground raid on a Yemeni village, killing dozens of civilians. The militant group denied that any militants were killed.
The group reported that the operation took place in al-Bayda governorate, which borders Shabwa, Site said. Last week, US drone strikes hit militants in al-Bayda, killing five over the course of three days. The militant group also reported it had shot down an American attack helicopter.
US officials said that an Osprey, a tilt-rotor military aircraft, went down in a "crash landing" at a staging area near the site of the operation but said the mishap was not believed to be caused by militant fire. The disabled Osprey was then intentionally destroyed. Two service members were injured in that landing. The Osprey had been sent to recovered the forces wounded in operation.
US Special Operations forces have maintained a small footprint in Yemen focused on Al-Qaeda in the Arabian Peninsula, which has been one of the most active branches of al-Qaeda and has been involved in plots to strike the West.
The last time US forces staged a raid on this scale was in December 2014, a few months before the country descended into civil war. But even before the war began, AQAP had seized large swaths of southern Yemen, taking advantage of the political turbulence after the Arab Spring revolts of 2011 toppled long-time Yemeni autocrat, Ali Abdullah Saleh.