Nato Secretary-General Anders Fogh Rasmussen said the alliance had seen what he called "a Russian incursion into Ukraine."
Responding to reports that a Russian column had entered Ukraine overnight, the Nato chief said: "It just confirms the fact that we see a continuous flow of weapons and fighters from Russia into eastern Ukraine and it is a clear demonstration of continued Russian involvement in the destabilisation of eastern Ukraine."
Mr Rasmussen also said Europe is becoming more dangerous and less stable.
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The Prime Minister said Parliament will be given a binding vote on the final deal, but said the result will not stop Britain leaving the EU.
Officials from the train drivers' union Aslef will meet managers from Southern Railway, whilst the RMT will meet separately with Acas.
Last week the organisation wrote on Twitter: "If Obama grants Manning clemency Assange will agree to US extradition".