The White House on Thursday called the attack on U.S. consulate in Libya's eastern city of Benghazi, in which four American diplomats were killed, a terrorist act.
"It is, I think, self-evident that what happened in Benghazi was a terrorist attack," White House spokesman Jay Carney told reporters aboard Air Force One en route to Florida.
"Our embassy was attacked violently, and the result was four deaths of American officials," he said.
The deaths of Ambassador Christopher Stevens and three of his staff on the night of Sept. 11 shocked the country. The attack was sparked ostensibly by a U.S.-made film that insults the Prophet Mohammed.
Addressing a hearing held on Wednesday by the Senate Homeland Security Committee, Matthew Olsen, director of the U.S. National Counterterrorism Center, discussed "indications of possible involvement of elements of extremist groups," including those from al-Qaeda and the group's affiliate in the Maghreb, Carney noted.
"I would point you to a couple of things that Mr. Olsen said, which is that at this point it appears that a number of different elements were involved in the attack, including individuals connected to militant groups that are prevalent in eastern Libya," Carney said.
He cited Olsen as saying that the attack, though not confirmed as a preplanned attack at the moment, "was the result of opportunism, taking advantage of and exploiting what was happening as a result of reaction to the video that was found to be offensive."
Prior to her appearance before both chambers of Congress for a closed-door hearing over the Benghazi attack on Thursday, U.S. Secretary of State Hillary Clinton told the press that she had formed an accountability review board to investigate the assault.
William Burns, Clinton's deputy, was in Libyan capital Tripoli on Thursday, where he met with the country's president, outgoing and incoming prime ministers and the foreign minister.
Burns reiterated Washington's position that responsible leaders need to do everything they can to restore security, reject violence, and hold accountable those responsible for the Benghazi attack, State Department spokeswoman Victoria Nuland said.
As anti-American protests are continuing in some parts of the world over the controversial film, Washington was buying airtime on all Pakistani TV stations to air an ad with a view to stemming the anger against the United States, as violent protests were raging on in the South Asian nation, Nuland said on Thursday at a press briefing.
Both President Barack Obama and Secretary Clinton were shown on the ad stating Washington's respect for all faiths as well as rejection of the film's content, a refrain they had repeated time and again since the Benghazi attack.
The ad was aired "to make sure that the Pakistani people hear the president's messages and the secretary's messages," Nuland said.