A detachment of 50 Marines was dispatched to secure the main American embassy in the Libyan capital Tripoli, where staff numbers were being cut to emergency levels, United States officials said.
The US also began evacuating all its staff from its mission in Benghazi, where 52-year-old Ambassador Chris Stevens, a fervent supporter of the revolt that overthrew Moamer Kadhafi, and three other Americans were killed on Tuesday.
At the same time two destroyers were sent to “the vicinity of Libya” as a precautionary measure, a senior US official said.
“Make no mistake, we will work with the Libyan government to bring to justice the killers who attacked our people,” US President Barak Obama said, while ordering increased security at US diplomatic missions around the world.
Tuesday’s assault on the US consulate in Benghazi followed a violent protest at the US embassy in Cairo over an amateurish anti-Islamic film made in the United States and reportedly promoted by a group of US-based Egyptian Copts.
“Make no mistake, we will work with the Libyan government to bring to justice the killers who attacked our people” – Obama.
Initial reports said Stevens and the three other Americans were killed by an angry mob as they tried to flee in a car.
But it is now believed that Stevens died from smoke inhalation after becoming trapped in the compound when suspected Islamic militants fired on the building with rocket-propelled grenades and set it ablaze.
US officials are investigating the possibility that the assault was a plot by Al-Qaeda affiliates or sympathisers, using the protests as a diversion to carry out a coordinated revenge attack on the 11th anniversary of 9/11.
US Secretary of State Hillary Clinton said the killings should “shock the consciences” of people of all faiths but vowed that the actions of “a savage and small group” would not make Washington turn its back on Libya.
Obama ordered security tightened at all US diplomatic missions, amid fears that anti-American protests sparked by the low-budget, privately produced film denigrating the Prophet Mohammed could spread.
There was no immediate conflagration around the Muslim world but new protests against the film were held on Wednesday outside US missions in Egypt, Morocco, Sudan and Tunisia. In Tunis, police fired tear gas to disperse a crowd of several hundred.