German Chancellor Angela Merkel insisted today that the European Union must maintain anti-Russian sanctions, even as EU foreign policy head Federica Mogherini wondered publicly how useful they might be.

Ms Merkel told a meeting of German employers in Berlin that her aim for Ukraine remains a diplomatic solution with Moscow.

However, she said that events at the weekend show "how difficult it is even to maintain agreements that have been made if we look at the illegal elections.

"Russia isn't yet contributing in the way we would like, particularly regarding Lugansk and Donetsk," she said.

"The Minsk agreement should be the basis. So the economic sanctions were inevitable and there is no reason at the moment to lift them."

Ms Mogherini, who succeeded Catherine Ashton as EU foreign policy high representative last month, said that the effect of sanctions on Russia's economy was clear to everyone.

However, "is that going to be the element that is going to change significantly the Russian political attitude towards the crisis?" she asked.

Alexander Zakharchenko was sworn in as prime minister of the self-proclaimed Donetsk People's Republic today in a ceremony coinciding with celebrations across Russia to mark National Unity Day.

Tens of thousands marched in Moscow bearing banners reading: "Crimea is ours" and "Novorussiya, we are with you."

Novorussiya refers to the Ukrainian regions that have opted for independence from Kiev.

Ukrainian Petro Poroshenko convened a crisis meeting of his security heads yesterday to discuss how to react to the weekend polls which he described as having jeopardised "the entire peace process."