LONDON (REUTERS) - Britain and Germany have agreed that the European Union should impose further consequences on Russia, building on travel bans and asset freezes agreed earlier by European foreign ministers, a spokeswoman for the British prime minister said.

Prime Minister David Cameron called German Chancellor Angela Merkel on Wednesday afternoon to discuss the EU's response to events in Ukraine ahead of a European Council meeting on Thursday, the spokeswoman said.

"They reiterated that Sunday's referendum in Crimea and Russia's subsequent actions to annex Crimea are both illegal and agreed that the EU should impose further consequences on Russia, building on the travel bans and asset freezes agreed by European foreign ministers on Monday," she said.

"They also agreed that the EU should keep working with the US and other international partners to de-escalate the situation and to deter Russia from embarking on any more action that could further destabilise Ukraine."

The two political leaders also agreed that the international community should do all it could to provide Kiev with the economic assistance it needed, saying that "a strong and successful Ukraine is in all our interests".