The new restrictions targeted an unspecified and unidentified number of people and entities that the Obama administration accused of threatening Ukraine's sovereignty and territorial borders.

On Tuesday, Putin said Russia had no intention of annexing Crimea, while insisting its residents have the right to determine the region's status in a referendum.

A referendum had previously been scheduled in Crimea on March 30, but the question to be put to voters was on whether their region should enjoy "state autonomy" within Ukraine.

Earlier, Crimea's new leader said pro-Russian forces numbering more than 11,000 now control all access to the peninsula in the Black Sea and have blockaded all military bases that have not yet surrendered.

The West has joined the new Ukrainian leadership in Kiev in demanding that Russia pull its forces back from Crimea, but little progress was reported after a flurry of diplomatic activity in Paris on Wednesday involving US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov.

Russia will face sanctions unless it withdraws its troops or engages in credible talks to defuse the situation, European leaders said on Thursday.

"We need to send a very clear message to the Russian government that what has happened is unacceptable and should have consequences," British Prime Minister David Cameron said as he arrived at an emergency meeting of the bloc's 28 leaders in Brussels.

AP - Reuters

Pro-Russian demonstrators hold rally in Donetsk	Negotiations on Ukraine crisis solution 'in right direction'