Missiles fired by a US drone slammed into a convoy of vehicles travelling to a wedding party in central Yemen, killing at least 17 people, Yemeni security officials said.
The officials said the attack took place on Thursday in the city of Radda, the capital of Bayda province, and left charred bodies and burnt out cars on the road.
The city, a stronghold of al-Qaeda militants, witnessed deadly clashes early last year between armed tribesmen backed by the military and al-Qaeda gunmen in an attempt to drive them out of the city.
There were no immediate details on who was killed in the strike, and there were conflicting reports about whether there were militants travelling with the wedding convoy.
A military official said initial information indicated the drone "mistook" the wedding party for an al-Qaeda convoy. He said tribesmen known to the villagers were among the dead.
One of the three security officials, however, said al-Qaeda militants were suspected to have been travelling with the convoy.
The CIA declined to comment on the reported strike, which is normal policy.
Civilian deaths have bred resentment, undermining US efforts to turn the public against the militants.
The backlash in Yemen is still not as large as in Pakistan, where there is heavy pressure on the government to force limits on strikes, but Yemeni public calls for a halt to strikes are starting to emerge.
In October, two UN human rights investigators called for more transparency from the IS and other countries about their drone programmes, saying their secrecy was the biggest obstacle to determining the civilian toll of such strikes.
The missile attacks in Yemen are part of a joint US-Yemeni campaign against al-Qaeda in the Arabian Peninsula, which Washington has called the most dangerous branch of the global terrorist network.
Thursday's drone strike was the second since a massive car bombing and co-ordinated assault on Yemen's military headquarters killed 56 people, including foreigners.
Al-Qaeda claimed responsibility for the attack, saying it was retaliation for US drone strikes that have killed dozens of the group's leaders.
Security forces in the Yemeni capital boosted their presence on Thursday, setting up checkpoints across the city and sealing off the road to the president's residence, in response to what the interior ministry called threats of "terrorist plots" targeting vital institutions and government buildings.
Meanwhile, in Yemen's restive north, ultraconservative Sunni Muslim militants and rebels belonging to a branch of Shiite Islam battled each other with artillery and machine guns in clashes that killed more than 40 people, security officials said.
The violence between Islamic Salafi fighters and Hawthi rebels has raged for weeks in the province of Saada, but the latest sectarian clashes marked an expansion of the fighting to the neighbouring province of Hagga. The government brokered a cease-fire last month to try to end the violence, but both sides have repeatedly broken the truce.