US military planes killed dozens of fighters at an Al-Qaeda affiliate's training camp in a mountainous region of Yemen, the Pentagon said.
The raids came almost one year since the Saudi-led Arab coalition launched its bombing campaign against Iran-backed Shiite rebels who challenged the authority of the Yemeni government and seized much of the country.
Yemeni government and tribal officials had earlier said Saudi-led air strikes killed or wounded dozens at a training camp in Hajr, west of Hadramawt's provincial capital Mukalla.
Fighters have held the city since April.
The early morning raid at a camp used by "more than 70" Al-Qaeda in the Arabian Peninsula fighters "deals a blow to AQAP's ability to use Yemen as a base for attacks that threaten US persons," Pentagon spokesman Peter Cook said in a statement.
"We continue to assess the results of the operation, but our initial assessment is that dozens of AQAP fighters have been removed from the battlefield," Cook said.
"It demonstrates our commitment to defeating Al-Qaeda and denying it safe haven."
It was not immediately clear whether there were any civilians among the casualties.
Tribal sources said wounded militants were taken to a hospital in Mukalla, while witnesses spoke of around nine vehicles rushing casualties out of the area.
Dozens of Al-Qaeda militants were meanwhile seen rushing to the hospital to donate blood, according to residents.
The World Health Organization says fighting in Yemen since March 2015 has claimed the lives of almost 6,300 people, while the UN human rights chief last week said half of all those killed were civilians with the vast majority of those deaths caused by coalition strikes.
Watchdogs Amnesty International and Human Rights Watch urged the United States, Britain and France to halt arm deliveries to Saudi Arabia that could be used in the Yemen conflict.
Riyadh launched the intervention in Yemen last year after Shiite Huthi rebels seized control of large parts of the country, including the capital Sanaa, and forced the government into exile.
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- Peace talks -
Loyalist forces backed by coalition strikes and ground troops have since retaken much of the south but have failed to dislodge the rebels from other areas including Sanaa.
They have recaptured second city Aden and the southern port has been declared the permanent seat of the government of President Abedrabbo Mansour Hadi.
But in the past few weeks, AQAP fighters and the self-proclaimed Islamic State group have bolstered their presence in southern and eastern Yemen.
The Sunni extremists were also reinforcing their grip on parts of Aden in defiance of the authorities and the Saudi-led coalition as the latter were busy pounding the Huthi rebels.
Last week, Saudi-led coalition warplanes struck the fighters in Aden, for the first time since the pro-government air campaign was launched on March 26 last year.
AQAP, which is well entrenched in Yemen where it has been active for years, is classified by the United States as Al-Qaeda's deadliest franchise and had claimed attacks on the West in the past.
It ruled the southern province of Abyan for a year before being driven out in June 2012. But in April, it seized Hadramawt's provincial capital Mukalla and nearby oil installations.
From Mukalla, AQAP has expanded to regain its foothold in southern provinces including Abyan last year and nearby Lahj and Shabwa.
Saudi Arabia launched the intervention in Yemen last year after Shiite Huthi rebels seized Sanaa and pushed southwards, forcing the government into exile.
Several rounds of UN-brokered peace talks have failed to nail a solution for Yemen.
But Yemeni Foreign Minister Abdulmalek al-Mikhlafi said he was "99 percent" sure a new round of talks would take place in Kuwait later this month.
A Yemeni government official said on Monday the peace negotiations would be accompanied by a ceasefire.
The union of journalists, meanwhile, accused rebels of killing cameraman Mohammed al-Yemeni in third city Taez while he was covering clashes.