The United States is dispatching a Marine fleet to boost security at the country’s consulate in Benghazi, Libya, where an armed group linked to al Qaeda struck late Tuesday killing four US diplomats including Ambassador Chris Stephens.

A Marine fleet anti-terrorist security team is being sent to the city, Reuters news agency quoted a U.S. official who spoke on the condition of anonymity.

No further details were immediately available.

In a televised speech at about 0230GMT following an earlier statement from the White House, President Barack Obama vowed to bring justice to the attackers, calling the killings “outrageous and shocking.”

“We’re working with the government of Libya to secure our diplomats,” Mr. Obama said at the Rose Garden, flanked by Secretary of States, Hilary Clinton. “And make no mistake; we will work with the Libyan government to bring to justice the killers who attacked our people.”

Armed men reportedly launched rocket propelled grenades at the US consulate building where Mr. Stevens, who resided in capital Tripoli, was visiting.

Reports say he died from suffocation after the militants launched an intense attack as he was being evacuated to safer grounds.

The attacks came in protest of an American-made amateurish trailer which portrays the Islam Prophet Muhammad in various offensive characters.

The film has sparked outrage in the Muslim world with the first protest occurring in Egyptian capital of Cairo on Tuesday.

Mr. Obama did not make reference to the Egypt protest where demonstrators tore an American flag and replaced it with an Islam flag.

The US president said the Benghazi attacks will not “break the bonds” between Libya and the United States.

He said Libyan security personnel fought back the attackers alongside Americans, helped American diplomats to safety, and carried Ambassador Stevens’ body to the hospital, where Mr. Stevens was confirmed dead.

“The world must stand together to unequivocally reject these brutal acts,” he said. “Already, many Libyans have joined us in doing so, and this attack will not break the bonds between the United States and Libya.”