More than 11,000 pro-Russian forces control all access to Ukraine's Crimean peninsula and have blockaded all military bases that have not yet surrendered, Crimea's new leader said.
Sergei Aksyonov said his administration is in regular contact with Russian officials, including those in a large Russian delegation now in Crimea.
Speaking at a Crimea government meeting, Mr Aksyonov said the strategic peninsula is fully under the control of riot police and security forces joined by thousands of "self-defence" troops.
All or most of these troops are believed to be Russian, even though president Vladimir Putin has denied sending in forces other than those stationed at the home port of Russia's Black Sea Fleet.
The West has joined the new Ukrainian leadership in Kiev in demanding that Moscow pull its forces from Crimea, but little progress was reported after a flurry of diplomatic activity in Paris yesterday involving US secretary of state John Kerry and Russian foreign minister Sergey Lavrov.
The European Union leaders are meeting for an emergency session in Brussels today to decide what sort of sanctions they can impose on Russia over its actions in Ukraine. Moscow has threatened to retaliate if any punitive measures are put in place.
A UN special envoy sent to Crimea came under threat from armed men who forced him to leave the region.
Robert Serry was threatened by 10 to 15 men as he was leaving naval headquarters in Crimea, said UN deputy secretary-general Jan Eliasson.
Concern that the turmoil could engulf eastern Ukraine grew after hundreds of demonstrators - many chanting "Russia! Russia!" - yesterday stormed a government building in Donetsk, a major industrial centre near the Russian border.
New clashes between protesters and police broke out today in Donetsk as police cleared demonstrators from the building. Dozens were detained.
The European Union has extended billion or euros in aid to help support the new Ukrainian government, which took over in late February after months of protests drove out Moscow-supported president Viktor Yanukovych.
The EU also imposed asset freezes against 18 people held responsible for embezzling state funds in Ukraine, including Yanukovych, his son and some of his closest allies.