Foreign Secretary William Hague has warned Russia it must allow planned elections in Ukraine to go ahead unimpeded if it wants to avoid damaging EU economic sanctions.

Following talks with EU foreign ministers in Brussels, Mr Hague dismissed weekend referendum votes staged by pro-Russian separatists in eastern Ukraine, saying they had no credibility or international acceptance.

"I think that the votes in the Eurovision Song Contest are more credible and carry greater weight than the circumstances of yesterday in Donetsk and in Luhansk," he said.

He said the ministers had widened existing EU travel bans and asset freezes to a further 13 individuals as well as two firms based in Crimea, which was effectively annexed by Moscow.

EU governments will now wait to see if Russia respects the Ukrainian presidential election - set by the government in Kiev for May 25 - before deciding whether to move to more far-reaching economic sanctions.

"It is the attitude and behaviour of all parties, including Russia, towards the holding of the elections on May 25 that will be a major determinant of whether such sanctions are necessary," Mr Hague said.

France's European affairs minister, Harlem Desir, said additional EU sanctions could be imposed if "actions and provocations" hamper the Ukraine presidential election campaign.