The US ambassador to the United Nations, Susan Rice, said on Sunday it began with a spontaneous protest over the anti-Islamic video that had already set off similar protests in Egypt, leading to the storming of the US embassy there.

“People gathered outside the embassy (consulate) and then it grew very violent and those with extremist ties joined the fray and came with heavy weapons, which unfortunately are quite common in post-revolutionary Libya and that then spun out of control,” Rice told Fox News Sunday.

“But we don’t see at this point signs this was a coordinated plan, premeditated attack. Obviously, we will wait for the results of the (FBI) investigation and we don’t want to jump to conclusions before then.”

Announcing the arrest of 50 suspects, Libya’s parliament chief, however, blamed the attack on a few foreign extremists who he said entered Libya from Mali and Algeria and pre-planned it with local “affiliates and sympathisers”.

“The way these perpetrators acted, and moved... leaves us with no doubt that this was pre-planned, determined, predetermined,” Mohammed Al Megaryef, president of the Libyan National Congress, told CBS News.

“It was planned, definitely, it was planned by foreigners, by people who entered the country a few months ago. And they were planning this criminal act since their arrival,” he added.

Ambassador Chris Stevens is believed to have died from smoke inhalation after being trapped in the blazing diplomatic compound in Benghazi, which came under fire from rocket-propelled grenades, mortars and small arms for several hours.

Al Qaeda in the Arabian Peninsula claimed the attack was revenge for the killing of the terror network’s deputy leader Sheikh Abu Yahya Al Libi in a drone strike in June, but there is no clear evidence to support this claim.

US authorities initially leaned more toward the premeditated, well-planned assault angle, citing the fact that the attack came on the anniversary of 9/11. But now they are more reticent, insisting that journalists wait for the results of the FBI investigation before leaping to any conclusions.

Rice’s comments are the strongest indication yet that — even if the United States does believe the assault was the work of a small band of extremists — it has no evidence to suggest planning prior to the protests.

But a leading Republican senator, John McCain, said it was ridiculous to believe this was anything other than a planned assault by extremists.

“Most people don’t bring rocket-propelled grenades and heavy weapons to a demonstration,” McCain told CBS’s “Fact the Nation”. —