A spokesman for the Coastguard has said that the search has been called off for the night and will resume tomorrow morning.
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The Foreign Secretary said the Kremlin's tit-for-tat expulsion of 23 British diplomats would only impact Vladimir Putin's compatriots.
Sunday will be bitterly cold with snow for most.
The current president looks set to win the election, with opposition leader Alexei Navalny barred from running.