WASHINGTON » In some respects, the drone strike in Yemen last week resembled so many others from recent years: A hail of missiles slammed into a group of trucks traveling by convoy on a remote 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 was at least a half-dozen innocent people and provoked a storm of 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 — and more transparent about the clandestine wars that President Barack Obama has embraced — 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.

Both 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 a reporter 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 strike’s aftermath said that one white pickup truck was destroyed and two or three other cars were seriously damaged. The Associated Press reported Friday that the target of the strike was Shawqi Ali Ahmed al Badani, a militant who allegedly planned a terror 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 that all the dead were militants. But Yemeni officials conceded soon afterward that some civilians had been killed, and gave 101 Kalashnikov rifles and about 24 million Yemeni riyals (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 that 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 during a speech on May 23 at the National Defense University — and whether such standards are even possible in such a remote and opaque environment.

In the speech, the president said that targeted killing operations are carried out only against militants who pose a "continuing and imminent threat to the American people." Over 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" — a bar 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 officials 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 desolate 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.

The very fact that last week’s drone strike targeted an 11-car convoy — a much larger group than al-Qaida would typically use — suggests that the new U.S. guidelines to rule out civilian casualties may not have been followed in this case.

And the confusion over the victims’ identities raises questions about how the U.S. government gathers intelligence in such a contested region and with partners whose interests may differ sharply from those of the Obama administration.

The area where the strike occurred, in the central province of Bayda, is almost completely beyond the control of the Yemeni government, and is populated by tribes whose recurring feuds can easily become tied up in the agendas of outsiders.

Over the past two years, the Saudi government — which has for decades used cash to maintain a network of influence in Yemen — has increased its payments to tribal figures in Bayda to recruit informers and deter militants, according to several tribal leaders in the area. This shadowy system appears to contribute to the secretive process of information-gathering that determines targets for drone strikes, a process in which Saudi and Yemeni officials cooperate with Americans.

But Saudi and U.S. interests diverge in important ways in Yemen. Many of the militants there who fight in al-Qaida’s name are expatriate Saudis whose sole goal is to bring down the Saudi government.

Because of the program’s secrecy, it is impossible to know whether the U.S. dependence on Saudi and Yemeni intelligence results in the killing of militants who pose a danger only to Arab countries.

Some Yemeni officials have also hinted that the timing and target of last week’s drone strike may have been influenced by a devastating attack two weeks ago on the Yemeni Ministry of Defense in which 52 people were killed, including women, children and doctors at the ministry’s hospital.

That attack ignited a desire for revenge in Yemen’s security establishment, and also damaged al-Qaida’s reputation in Yemen, leaving the group hungry for opportunities to change the subject. Both parties, in other words, may have had reasons to manipulate the facts, both before and after the drone strike.

U.S. officials will not say what they knew or did not know about the targets of last week’s strike. But in the past, U.S. officials have sometimes appeared to be misinformed about the accidental deaths of Yemeni civilians in drone strikes.

In one example from Aug. 1, a drone strike killed a 28-year-old man who happened to hitch a ride with three suspected al-Qaida members. According to a number of witnesses, relatives and local police officials, the man, Saleh Yaslim Saeed bin Ishaq, was waiting by a gas station late at night when three men stopped in a Land Cruiser, and agreed to give him a lift.

Ishaq’s ID card and belongings were found in the burned wreckage of the vehicle, and the local police — who confirmed that the other three dead men were wanted militants — said he appeared to be an innocent whose presence in the car was accidental.

When contacted about the strike, U.S. officials said they were aware only of the three militants killed. Yet the details of Ishaq’s death, and an image of his ID card, were printed at the time in Yemeni newspapers and websites.

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Mark Mazzetti And Robert F. Worth, New York Times

© 2013 The New York Times Company