WASHINGTON (Reuters) - The U.S. Federal Aviation Administration issued an order on Thursday night prohibiting American aircraft from flying over eastern Ukraine following the downing of a Malaysia Airlines flight in that region.

Citing "recent events and the potential for continued hazardous activities," the FAA said the restricted area included the entire Simferopol and Dnepropetrovsk flight information regions. "This action expands a prohibition of U.S. flight operations issued by the FAA in April, over the Crimean region of Ukraine and adjacent areas of the Black Sea and the Sea of Azov," the agency said.

It added that no scheduled U.S. airlines were currently flying routes through the airspace.

Earlier in the day, the FAA said American air carriers had voluntarily agreed to avoid flying through airspace near Russia's border with Ukraine after the crash.

The FAA said its April order, known as a Notice to Airmen, was prompted by "unilateral and illegal action by Russia to assert control over Crimean airspace," including international airspace administered by Ukraine. In March, Russia annexed Crimea.

The FAA said Russia's actions at the time had created "the potential for conflicting air traffic control instructions from Ukrainian and Russian authorities" and a risk of civil aircraft being misidentified by authorities.

The FAA's April order also warned U.S. operators and pilots flying in other parts of Ukraine, including Kiev, Lvov, Dnepropetrovsk and Odessa, to "exercise extreme caution due to the continuing potential for instability."

The FAA said that its April order, which will remain in effect until April 23, 2015, did not cover the specific airspace where the Malaysian flight went down on Thursday.


(Additional reporting by Alwyn Scott; Editing by Ken Wills)