The European Space Agency, which launched the Rosetta mission, is preparing for an event in Germany to mark the spacecraft's arrival at an icy comet.
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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.