WASHINGTON — In some respects, the drone strike in Yemen last week resembled so many others from recent years: A barrage of missiles slammed into trucks traveling by convoy on a desert road, killing at least 12 people.

But this time the trucks were part of a wedding procession, making the customary journey from the groom’s house to the house of the bride.

The Dec. 12 strike by the Pentagon — launched from a U.S. base in Djibouti — killed what multiple sources in Yemen say were at least six innocent people and provoked outrage in the country. It also illuminated the reality behind the rhetoric surrounding the Obama administration’s new drone policy that was announced with great fanfare six months ago.

Although U.S. officials say they are being more careful before launching drone strikes in Yemen, Pakistan and elsewhere, last week’s strike offers a troubling window on the intelligence breakdowns and continuing liability of a targeted killing program that remains almost entirely secret.

The Pentagon and the CIA 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 to a vague news release issued last week by the government of Yemen, written in Arabic.

Who the Americans were trying to kill in the strike, carried out in a desolate area southeast of Yemen’s capital, remains unclear. Witnesses to the aftermath said one white pickup was destroyed and two or three other cars were seriously damaged.

The Associated Press reported Friday the target was Shawqi Ali Ahmad al-Badani, a midlevel leader in al-Qaida in the Arabian Peninsula who allegedly was behind a terrorist plot in August that led to the closing of more than a dozen U.S. embassies. U.S. officials declined to comment about that report.

At first, the Yemeni government, a close partner with the Obama administration on counterterrorism matters, said all the dead were militants. But Yemeni officials conceded soon afterward that some civilians had been killed, and gave 101 Kalashnikov rifles and about $110,000 to a mediator, who, in accord with Yemeni custom, will help determine how many people should be compensated.

Yemeni government officials and several local tribal leaders said the dead included several militants with ties to al-Qaida’s Yemen-based branch, 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 U.S. officials are applying the standards for lethal strikes that Obama laid out May 23 and whether such standards are even possible in such a remote and opaque environment.

In the speech, the president said targeted killing operations are carried out only against militants who pose a “continuing and imminent threat to the American people.” In the past week, no government official has made a case in public that the people targeted in the strike posed a threat to Americans.

Moreover, the president said in May, no strike can be authorized without “near certainty that no civilians will be killed or injured,” which he described as “the highest standard we can set.”

At the time, administration officials said that authority over the bulk of drone strikes would gradually shift from the CIA to the Pentagon, a move they said was designed partly to lift the shroud of secrecy from the targeted killing program.

But nearly seven months later, the CIA still carries out a majority of drone strikes in Yemen, with the remote-controlled aircraft taking off from a base in the southern desert of Saudi Arabia. The Pentagon strikes, usually launched from the Djibouti base, are cloaked in as much secrecy as those carried out by the CIA.

“The contradictory reports about what happened on Dec. 12 underscore the critical need for more transparency from the Obama administration and Yemeni authorities about these strikes,” said Letta Tayler, of Human Rights Watch, who has done extensive research in Yemen about the drone strikes.