WASHINGTON -- The violent deaths of four U.S. diplomats in Libya during a heavily armed and possibly planned assault on a consulate facility on the Sept. 11 anniversary provoked a crisis in Washington on Wednesday.
President Obama denounced the attack, promised to avenge the killings, and ordered tighter security at all U.S. diplomatic installations.
The administration ordered all nonemergency personnel to leave Libya and warned Americans not to travel there.
In a show of force, the Pentagon moved two warships to the Libyan coast.
Officials said one destroyer, the USS Laboon, moved to a position off the coast Wednesday, and the destroyer USS McFaul was en route and should be stationed off the coast within days, increasing the number of Navy destroyers in the Mediterranean from four to five.
Officials said the ships, which carry Tomahawk cruise missiles, do not have a specific mission.
But they give commanders flexibility to respond to any mission ordered by the President.
"Without commenting on specific ship movements, the United States military regularly takes precautionary steps when potential contingencies might arise in a given situation," said Pentagon spokesman George Little. "That's not only logical in certain circumstances, it's the prudent thing to do."
At the same time, 50 U.S. Marines headed to Libya to reinforce security at U.S. diplomatic facilities, initially at the American embassy in Tripoli, not Benghazi.
"These four Americans stood up for freedom and human dignity," Mr. Obama said in a televised statement from the White House Rose Garden, where he stood with Secretary of State Hillary Clinton. "Make no mistake: we will work with the Libyan government to bring to justice the killers who attacked our people."
Republican presidential challenger Mitt Romney criticized Mr. Obama's handling of the attacks.
"It's never too early to condemn attacks on Americans and to defend our values," Mr. Romney said at a campaign office in Jacksonville, Fla. He condemned the violent protests and expressed condolences to the families of those slain in Libya.
Initial accounts of the assault in Benghazi were attributed to anger over what was described as a U.S.-made video that lampooned the Prophet Mohammed, which had been publicized by Egyptian media and led to a mob protest at the U.S. Embassy in Cairo on Tuesday.
In an extraordinary move, Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, called anti-Islamic preacher Terry Jones Wednesday and asked him to stop promoting the film. A spokesman said the church would not show the film Wednesday evening.
While the protesters in Cairo appeared to be genuinely outraged over the anti-Islam video, however, the attackers in Benghazi were armed with mortars and rocket-propelled grenades.
Officials said it was possible that an organized group had either been waiting for an opportunity to exploit, like the protests over the video, or perhaps even generated the protests as a cover for their attack.
In a dispatch from Benghazi, Reuters quoted witnesses as saying the attackers included tribesmen, militia, and other gunmen, and that Libyan security officers guarding the facility were overrun and some retreated.
White House press secretary Jay Carney said it was too early to judge whether the Benghazi attack was planned.
One official said it was too early to assign responsibility to a militant group like Ansar al-Sharia, the focus of much attention on Wednesday.
The official likewise said it was not known whether the attack had been intended to coincide with the anniversary of the Sept. 11 attacks.
"Motivation remains a mystery," the official said.
Moreover, the official pointed out that weapons are commonplace in that part of Libya and it was possible that as anger over the video mushroomed, radicals armed themselves and rushed to the consulate on their own.
"This is Benghazi," the official said. "This is the wild west."
The chaotic scene was described by senior Obama Administration officials, Libyan government officials, and eyewitnesses.
At least an hour before the assault in Benghazi began, a stream of cars reportedly moved toward the U.S. Consulate in the eastern Libyan city.
By late evening, as many as 50 heavily armed militants had gathered outside its high walls.
They joined protesters outside the consulate who were demonstrating against an American movie that they believed denigrated the prophet Mohammed.
But according to one witness, the new arrivals neither chanted slogans nor carried banners.
"They said, 'We are Muslims defending the prophet. We are defending Islam,' " Libyan television journalist Firas Abdelhakim said in an interview.
The gunmen soon opened fire, entered the compound, and set the consulate's buildings aflame. Hours later, the compound was overrun and four Americans were dead.
Among them were U.S. Ambassador J. Christopher Stevens, 52, and Sean Smith, a State Department employee.
There were conflicting accounts of how Mr. Stevens had died.
One witness to the mayhem around the compound Tuesday said militants chased him to a safe house and lobbed grenades at the location, where he was later found unconscious, apparently from smoke inhalation, and could not be revived by rescuers who took him to a hospital.
An unidentified Libyan official in Benghazi told Reuters that Mr. Stevens and three staff members were killed in Benghazi "when gunmen fired rockets at them."
The Libyan official said the ambassador was being driven from the consulate building to a safer location when gunmen opened fire, Reuters said.
Rep. Mike Rogers (R., Mich.), chairman of the intelligence committee, said the assault appeared to be well planned and well organized, with attackers executing military-like maneuvers.
"We haven't seen any significant indication of al-Qaeda involvement in this attack," a senior U.S. intelligence official said, adding that there are conflicting indications of the extent to which it was planned.
"We've seen some indications that point us in that direction and others that do not," said the official, who spoke on the condition of anonymity.
U.S. officials said the CIA, the FBI and other agencies were mobilizing to identify and pursue the attackers, an effort that could be aided by U.S. drones that have continued to conduct surveillance flights over the country since Tripoli fell 13 months ago.
Officials said the assault may have been carried out by an affiliate of al-Qaeda, perhaps seeking to avenge the death of a Libyan who had served as the terrorist group's No. 2 operative until he was killed in Pakistan in June by a U.S. drone strike.
Mr. Obama ordered increased security at all U.S. diplomatic missions overseas, particularly in Libya, and said he condemned "in the strongest possible terms the outrageous and shocking" attack.
Mrs. Clinton said she was particularly appalled that the attack took place in Benghazi, which the United States had helped liberate from dictator Moammar Gadhafi during the Arab Spring revolution in Libya last year.
Three Americans were wounded, U.S. officials said.
"This is not easy," she said. "Today, many Americans are asking, indeed I asked myself, how could this happen? How could this happen in a country we helped liberate, in a city we helped save from destruction? This question reflects just how complicated and, at times, just how confounding, the world can be."
"But we must be clear-eyed in our grief," she said, saying the attack was carried out by a "small and savage group" not representative of the Libyan people.
She noted that Libyan security guards had tried to fight off the attackers and had led other consulate employees to safety.
Top Libyan officials, including the interim leader, quickly apologized and vowed to help find the killers.