UK Foreign Secretary William Hague has revealed that talks between Russia and the US over the Ukraine crisis are to be held in London, ahead of a referendum on the annexation of Crimea.

Hague tweeted the following message:

The message was sent after a call between Hague and German foreign minister Frank-Walter Steinmeier, in which the latter warned Russia that there would be a tough European Union response should the proposed referendum take place.

The British foreign secretary also spoke with his US counterpart, saying that ministers in Washington and London are collaborating on the Ukraine crisis.

German Chancellor Angela Merkel has warned Russia that it will face "massive damage" if it continues on its course over Ukraine.

"If Russia continues on its course of the past weeks, it will not only be a catastrophe for Ukraine. We would not only see it, also as neighbours of Russia, as a threat. And it would not only change the European Union's relationship with Russia.

"No, this would also cause massive damage to Russia, economically and politically," she said.

The Crimean parliament has voted to join Russia and will put the case to voters in a referendum on 16 March. Crimeans will be asked to vote on whether the republic should join Russia or remain part of Ukraine.

In reaction, Nato has dispatched Awacs [Airborne Warning and Control System] reconnaissance aircrafts to Poland and Romania in order to monitor the Ukraine border after authorisation was granted by alliance ambassadors.

Despite the crisis, Russian President Vladimir Putin's approval ratings have reached a three-year high following the occupation of Crimea and the Sochi Winter Olympics, according to a Russian poll.