WASHINGTON — Secretary of State Hillary Clinton and the White House on Wednesday downplayed reports that a Libyan group claimed responsibility on Facebook for the deadly strike on the US consulate in Benghazi.

US ambassador Christopher Stevens and three other Americans were killed in the September 11 attack, for which the hardline Salafist group Ansar al-Sharia allegedly took blame on the social networking site.

"Posting something on Facebook is not, in and of itself, evidence," Clinton told reporters.

Clinton commented when asked about US media reports claiming that the State Department informed the White House via email just hours after the attack that Ansar Al-Sharia had claimed responsibility.

White House spokesman Jay Carney, asked about the issue while on the campaign trail with President Barack Obama, said "there were emails about all sorts of information that was coming available in the aftermath of the attack." "This is an open source, unclassified email about a posting on a Facebook site. I would also note that within a few hours the organization itself claimed that it had not been responsible. Neither should be taken as fact. That is why there is an investigation," Carney said.

State Department spokeswoman Victoria Nuland also acknowledged the email traffic between the State Department and other government offices concerning the Benghazi attack.

"This was one piece of unclassified information that had been posted on a Facebook page, among many, many, many pieces of information that were coming in that evening, afterwards, from all over the place, both classified and unclassified," said Nuland. "So one can't weigh these things in their totality without looking at all of them."

The Benghazi attack has triggered a political firestorm in the United States ahead of the November 6 presidential election. Opposition Republicans led by Mitt Romney have blasted the Obama administration, accusing his administration of huge security failures and of trying to cover up the circumstances of the assault.