Missiles fired by a U.S. drone slammed into a convoy of vehicles traveling to a wedding party in central Yemen on Thursday, killing at least 13 people, three Yemeni security officials said.

The officials said the attack occurred 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 as armed tribesmen backed by the military attempted to drive al-Qaeda gunmen out of the city.

Details on who was killed in Thursday’s strike were not immediately available, and there were conflicting reports about whether militants were traveling with the wedding convoy.

A military official said initial information indicated that 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 security officials, however, said al-Qaeda militants were suspected to have been traveling with the convoy.

The CIA declined to comment on the drone strike. Although the United States acknowledges its drone program in Yemen, it does not usually talk about individual strikes.

If further investigations determine that all the victims were civilians, the attack could fuel anger against the United States and the government in Sanaa among a Yemeni public already opposed to U.S. drone strikes.

Civilian deaths have bred resentments on a local level, sometimes undermining U.S. efforts to turn the public against the militants. The backlash in Yemen is still not as large as in Pakistan — but public calls for a halt to drone strikes are starting to emerge.

The missile attacks in Yemen are part of a U.S.-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 is the second since a car bombing and coordinated assault on Yemen’s military headquarters last week killed 56 people, including foreigners. Al-Qaeda asserted responsibility for that attack, saying it was retaliation for U.S. drone strikes that have killed dozens of the group’s leaders.

Security forces in the Yemeni capital boosted their presence 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 Salafist fighters and Houthi rebels has raged for weeks in the province of Saada, but the latest sectarian clashes marked an expansion of the fighting to the neighboring province of Hajjah.

— Associated Press