Russia's energy giant Gazprom said Ukraine had failed to pay at least part of its gas debts by this morning's deadline and must now pay up front for its energy supplies.
Gazprom said Ukraine has not yet paid for June supplies. The two countries failed to reach a deal on gas prices.
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Cloud and outbreaks of rain will ease away eastwards during the morning, clearing the east coast around midday with sunny spells developing.
Police and emergency services are attending the scene.
Rebel-held east remains at risk while the pumping station supplying the western part of the city is once again in operation.