BRUSSELS (REUTERS) - The secession referendum in Ukraine's Crimea is illegal and illegitimate and its outcome will not be recognised, The European Union's top officials said in a joint statement on Sunday.

European Commission President Jose Manuel Barroso and European Council President Herman Van Rompuy also called on Russia to withdraw its armed forces to their pre-crisis numbers and to usual areas of deployment.

EU foreign ministers will decide on possible measures at a meeting in Brussels on Monday.