The State Department is telling all U.S. citizens in Libya to leave immediately because of what it calls an "unpredictable and unstable" security situation.
A travel warning issued late Tuesday says the Libyan government has not adequately built a military and police force, and that many military-grade weapons are in the hands of civilians. It says this includes anti-aircraft weapons that could be aimed at civilian aircraft.
The warning says foreigners in Libya are generally presumed to be associated with the U.S. government and may be the targets of kidnappers or killers.
Earlier Tuesday, a Pentagon official said the aircraft carrier USS Bataan is being deployed to the Mediterranean in case an evacuation of Americans from Libya is needed.
Armed groups stormed the Libyan congress last week and Islamist militants have warned the U.S. not to interfere.