The EU foreign affairs representative, Catherine Ashton, said that if Russia does not step down forces the EU will "decide about consequences," meaning targeted economic sanctions.
News agency AFP quotes Sweden's foreign minister, Carl Bildt, as saying "Some in Russia are still impressed by their military might...That is not the way to make friends in Europe, in the world."
Ukranian officials say their units in the Crimea have been given an ultimatum by Russian forces to disarm, or face attack. This has been denied by Russian officials.
To news agency TT Carl Bildt says the EU has soft power that can influence Russia, including making an economic impact.
"Look at what the financial markets have done with the rouble and with Russian assets today. If it continues it will of course get even worse."