The United States has evacuated all of its diplomatic personnel from the eastern Libyan city of Benghazi following the killing of the U.S. ambassador to Libya and three consulate employees, a senior administration official of the U.S. Department of State said.

Ambassador Chris Stevens and three other Americans were killed on Tuesday after the diplomatic facility in Benghazi was attacked by an armed mob angry over a U.S.-produced film that is said to be insulting to Islam's Prophet Muhammad.

“This evacuation, which had to occur in a couple of planeloads, included all of our American Benghazi personnel, including the three wounded, and the remains of our fallen colleagues. They are now in the process… of being evacuated to Germany,” the official said.

He added that the diplomatic personnel of the U.S. Embassy in the Libyan capital of Tripoli were also partly evacuated with a minimum number of diplomats remaining there.

“We have taken our Embassy in Tripoli down to emergency staffing levels. We have reduced the staff down to what we call emergency staffing levels. And we have requested increased support from the Libyans while we assess the security situation,” he said.

U.S. President Barack Obama condemned the attack and the killings and ordered “all necessary resources to support the security of our personnel in Libya, and to increase security at our diplomatic posts around the globe."

Stevens had been paying a brief visit to the city, which was the stronghold of resistance against the rule of late former leader Muammar Gaddafi, who was killed by rebel militia in October last year.

Libyan Ambassador to the United States Ali Aujali put the blame for the attack on supporters and sidekicks of slain Gaddafi, while the U.S. intelligence service initially reported that the attack was linked to al-Qaeda.

Protesters also attacked on Tuesday the U.S. consulate in the Egyptian capital Cairo.

The incidents occurred on the 11th anniversary of the 9/11 attacks in the United States.

The video that triggered the attacks, Innocence of Muslims, has been actively promoted by a Florida pastor, Terry Jones, who gained notoriety for threatening to burn and then burning a Koran that set off riots in Afghanistan in 2010 and 2011, the New York Times reported.