WASHINGTON -- The assault on the U.S. diplomatic mission in Benghazi last month appears to have been an opportunistic attack rather than a long-planned operation, and intelligence agencies have found no evidence that it was ordered by al-Qaida, according to U.S. officials and witnesses interviewed in Libya.
The circumstances of the Sept. 11 attack have become a matter of heated political debate, with President Barack Obama and Republican nominee Mitt Romney clashing in their debate Tuesday about when Mr. Obama termed the assault an act of terrorism. But the emerging picture painted by intelligence officials and witnesses differs from the assertions of both sides.
Republicans have zeroed in on possible al-Qaida ties to the Sept. 11 attack that killed Ambassador J. Christopher Stevens and three other Americans, and have criticized the Obama administration for not saying early on that it was an act of terrorism. But after five weeks of investigation, U.S. intelligence agencies say they have found no evidence of al-Qaida participation.
The attack was "carried out following a minimum amount of planning," said a U.S. intelligence official, who, like others, spoke on condition of anonymity to discuss a matter still under investigation. "The attackers exhibited a high degree of disorganization. Some joined the attack in progress, some did not have weapons and others just seemed interested in looting."
A second U.S. official added, "There isn't any intelligence that the attackers pre-planned their assault days or weeks in advance." Most of the evidence so far suggests that "the attackers launched their assault opportunistically after they learned about the violence at the U.S. Embassy in Cairo" earlier that day, the official said.
The lack of a firm al-Qaida link could constrain U.S. military options. The administration believes that it has the right under international law to use lethal force against al-Qaida operatives who kill Americans, but that case would be harder to make against members of a Libyan militia.
The description by witnesses also differs from some recent administration statements.
Officials, most notably Susan Rice, the U.S. ambassador to the United Nations, at first said they believed that the attack was motivated by a controversial anti-Islamic video made in the United States. More recently, officials downplayed any connection.
But in Benghazi, witnesses said members of the group that raided the U.S. mission specifically cited the video, which denigrated the prophet Muhammad.
Tarek, an off-duty police sergeant who asked that his full name be withheld to shield him from reprisals, said he came to the scene about an hour after the attack began and found militants blocking the road leading to the compound. "They drew their guns on me, and they told me that the Americans were abusing our prophet," he said. "That's why they said they had come to fight."
He and others described the attackers as a mob, rather than a team of commandos. It included some organized elements, they said, but its intelligence was less than precise. A caretaker at the villa adjacent to the U.S. mission said the attackers initially threatened to raid his compound until he and a guard barred the gate and shouted: "Private property! Women inside!"
Libyan guards who served as the U.S. compound's security force said the mob was made up of disparate types, some of whom appeared to be experienced fighters and others not. There were long-bearded men whose faces were obscured by scarves, in the style of practiced militants, who called each other "sheik." But there also were younger men, some of whom appeared to be teenagers, with wispy beards on their uncovered faces.
"There were civilians there, and many were carrying weapons," said Sheik Mohamed Oraibi, a hard-line Islamic preacher who arrived soon after the attack began. He said the attackers arrived in about 20 pickup trucks, many of which had machine guns mounted on them in the style favored by rebels during the Libyan revolution last year.
Multiple witnesses said the accents and vernacular used by the attackers sounded Libyan, not foreign. They were extremely well-armed, but Libya is awash in weapons. In Benghazi, machine guns and shoulder-fired grenade launchers, many of them pilfered by rebels from stocks of the late deposed dictator Moammar Gadhafi during the revolution, are sold on the streets.
"This was a group of thieves that saw a chance and wanted to seize it," said Hamad Bougrain, a spokesman for the Feb. 17 Martyrs Brigade, a Libyan pro-government militia whose members were part of the U.S. mission's security detail. The militia members also responded to the attack.
Libyan officials say one of the key suspects is Ahmed Abu Khattala, leader of an Islamist militia called the Abu Obeida brigade. He has acknowledged being at the scene but denies leading the raid. Libyan officials say there are no orders to arrest him.
U.S. intelligence and special operations planners have been preparing so-called target packages on militants suspected of involvement in the attacks -- dossiers that are often the prelude to a kill-or-capture operation.
Ms. Rice has been widely criticized for comments she made on a round of talk-show appearances Sept. 16, when she said the attack appeared to have stemmed from a protest against the video, similar to the violent demonstration at the Cairo embassy.