SANA'A, Yemen - 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, Yemeni security officials said.

The officials said the attack took place in Radda, the capital of Bayda province, and left charred bodies and burned-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 traveling 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 traveling with the wedding convoy.

The CIA declined to comment on the reported strike. While the U.S. acknowledges its drone program in Yemen, it does not usually address individual strikes.

If further investigations determine that the victims were all civilians, the attack could fuel an outburst of anger against the United States and the government in Sana'a among a Yemeni public already opposed to 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, where there is heavy pressure on the government to force limits on strikes - but public calls for a halt to strikes are starting to emerge.

In October, two U.N. human-rights investigators called for more transparency from the United States and other countries about their drone programs, saying their secrecy is the biggest obstacle to determining the civilian toll of such strikes.

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 massive car bombing and coordinated assault on Yemen's military headquarters killed 56 people, including foreigners. Al-Qaeda claimed responsibility.

Meanwhile, in Yemen's restive northern, ultraconservative Sunni Muslim militants and rebels belonging to a branch of Shiite Islam battled each other with artillery and machine guns, killing more than 40 people, security officials said.