The US government is investigating whether the attack on the consulate in Benghazi, Libya, was a planned terrorist strike to mark the anniversary of the September 11 attacks rather than a spontaneous mob enraged over the anti-Islam video on YouTube.
President Barack Obama said the US would "work with the Libyan government to bring to justice" those who killed Chris Stevens and three other Americans. It was the first killing of a US ambassador in more than 30 years.
The attack on the Benghazi consulate was "a planned, co-ordinated, well-executed military style event", House of Representatives Intelligence Committee chairman Mike Rogers said.
In a show of force, the Pentagon has moved two warships to the Libyan coast. Officials said one destroyer, the USS Laboon, moved to a position off the coast yesterday and the destroyer USS McFaul was on its way and should be stationed off the coast within days, increasing the number of US 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. At the same time, around 50 US Marines headed to Libya to reinforce security at US diplomatic buildings, initially at the American embassy in Tripoli.