There appears to be some urgency to this State Department advisory that US citizens leave Libya "immediately." They previously recommended no travel outside of Tripoli and that Americans should exercise "extreme caution" when moving about.

Associated Press:

"U.S. citizens currently in Libya should exercise extreme caution and depart immediately," the department said in a statement.

The department in December warned U.S. citizens against all but essential travel to Tripoli, and against any travel outside the Libyan capital.

Since then a renegade Libyan general has launched a military offensive against Islamists and their allied militias in Libya, which has been plagued by lawlessness since the death of dictator Moammar Gadhafi in 2011.

Also Tuesday, U.S. defense officials said the Navy warship USS Bataan had moved into the Mediterranean Sea and could be used, if needed, for any possible evacuation of American personnel from Libya.

The officials said the Bataan, an amphibious assault ship, was not near Libya and wasn't expected to be positioned off its coast. It more likely would remain in the region, and could move or respond quickly if called.

The officials spoke on condition of anonymity because they were not authorized to discuss the matter by name.

The rogue Libyan General Haftar may be fighting the Islamists, but he is also in conflict with the western backed government. Haftar spent his exile in Virginia and it's believed he is close to the CIA. This isn't sitting well with Islamists or Libyan nationalists who make up the more secular opposition to the government. But the fact that Haftar is taking on the Muslim Brotherhood and al-Qaeda has given him a growing following as many Libyans are alarmed at the government's paralysis in going after the terrorists.

This has led to a very chaotic and dangerous situation for any foreigner, but especially Americans. It could also be that the State Department has gotten some hard intelligence that Americans have become targets of one or more of the many Islamist groups who roam freely in the capital and elsewhere.

The Islamist parliament recently approved a new government, defying threats from Haftar and other allied militias. It seems probable that a showdown is coming and Americans should heed the warnings of the State Department and get while the going is good.