President Obama says the U.S. is imposing unilateral sanctions on Libya because continued violence and unrest there poses an "unusual and extraordinary threat" to America's national security and foreign policy.

He says a series of financial sanctions he formalized on Friday target the government of Libyan leader Moammar Gadhafi  while protecting the Libyan people's assets. The penalties name Gadhafi and several family members.

 Obama acted after hundreds of Americans were safely evacuated from Libya following days of bloodshed across the country. Militias loyal to Gadhafi have been firing on protesters who have been demanding the Libyan leader's ouster.

White House spokesman Jay Carney said earlier Friday that the U.S. would impose unilateral sanctions and continue to work with its European partners on additional punishments that could be taken.