The United States ordered Saturday's evacuation of its embassy in Libya due to a "very real risk" to personnel, Secretary of State John Kerry said.

Kerry said that the United States sent its embassy personnel overland to Tunisia "because of the freewheeling militia violence that is taking place in Tripoli."

"A lot of the violence is around our embassy -- but not on the embassy -- but nevertheless presents a very real risk to our personnel," he told reporters in Paris.

Kerry said that the United States was "suspending" operations but not closing the embassy in the Libyan capital, pledging that Washington would stay focused on the country's troubles.

"We will return the moment the security situation permits us to do so. But given the situation... we want to take every precaution to protect our folks," Kerry said.

President Barack Obama's administration faced intense domestic criticism over its handling of a 2012 attack on the US consulate in the eastern Libyan city of Benghazi, which killed four Americans including the ambassador, Chris Stevens.

The United States joined France and Britain in a 2011 military campaign in support of an uprising that ousted strongman Moamer Kadhafi.

"We call on all Libyans to engage in the political process and to come together in order to avoid the violence. So many people died and gave so much effort to the birth of the new Libya," Kerry said.