Both the Pentagon and the C.I.A. continue to wage parallel drone wars in Yemen, but neither is discussed publicly. A Pentagon spokeswoman declined to comment about the Dec. 12 strike, referring a reporter to a vague news release issued last week by the government of Yemen, written in Arabic.

It remains unclear whom the Americans were trying to kill in the strike, which was carried out in a desolate area southeast of Yemen’s capital, Sana. Witnesses to the strike’s aftermath said that one white pickup truck was destroyed and that two or three other vehicles were seriously damaged. The Associated Press reported Friday that the target of the strike was Shawqi Ali Ahmad al-Badani, a militant who is accused of planning a terrorist plot in August that led to the closing of more than a dozen United States Embassies. American officials declined to comment about that report.

At first, the Yemeni government, a close partner with the Obama administration on counterterrorism matters, said that all the dead were militants. But Yemeni officials conceded soon afterward that some civilians had been killed, and they gave 101 Kalashnikov rifles and about 24 million Yemeni riyals (about $110,000) to relatives of the victims as part of a traditional compensation process, a local tribal leader said.

Yemeni government officials and several local tribal leaders said that the dead included several militants with ties to Al Qaeda’s branch in Yemen, but no one has been able to identify them. Some witnesses who have interviewed victims’ families say they believe no militants were killed at all.

The murky details surrounding the strike raise questions about how rigorously American officials are applying the standards for lethal strikes that Mr. Obama laid out in a speech on May 23 at the National Defense University — and whether such standards are even possible in such a remote and opaque environment.