The European Union has agreed to step up sanctions against Russia over Ukraine by expanding a list of people targeted with asset freezes and visa bans.

Member states could hold an emergency summit next week to adopt further measures.

EU foreign ministers acted in response to a deepening of the crisis in Ukraine, where pro-Russian separatists ignored an ultimatum on Monday to leave occupied government buildings.

"We have agreed ... to expand the sanctions," Foreign Secretary William Hague told reporters in Luxembourg.

EU officials will now begin work on a list of new names of people who they believe played a role in violating Ukraine's territorial integrity. They will be added to a list of 33 Russian and Ukrainian officials already under EU asset freezes or visa bans.

The ministers again held out the threat of imposing tougher sanctions on Russia, such as trade and financial restrictions, if Moscow took further steps to destabilise Ukraine. Any further tightening of sanctions will likely depend on the outcome of a meeting between the EU, the United States, Russia and Ukraine planned for Geneva on Thursday.

"There may be a meeting of heads of state and government next week at European level, which may adopt new sanctions," French foreign minister Laurent Fabius said.