Poroshenko: Ukraine 'close to point of no return'
Baroness Ashton said there was "deep concern" over "direct aggression by Russian forces". She called on Russia to stop the flow of arms, equipment and personnel into Ukraine.
As she arrived at the talks in Brussels, Lithuanian President Dalia Grybauskaite said Russia was "practically in a war against Europe".
UK Prime Minister David Cameron said the EU faced "a completely unacceptable situation of having Russian troops on Ukrainian soil. Consequences must follow if that situation continues".
French President Francois Hollande said the Ukraine crisis was the biggest since the end of the Cold War.
He said: "What's happening in Ukraine is so serious that the European Council will be obliged to react by increasing the level of sanctions if things remain as they are."MH17 crash: John Alder's body identified
Mr Alder, who was 63, died alongside fellow Newcastle fan Liam Sweeney and 296 others when the plane was shot down over Ukraine on 17 July.
Western politicians suspect the jet was hit by a Russian surface-to-air missile fired by pro-Russian separatists.Ukraine overshadows EU summit
EU leaders have been meeting in Brussels to discuss the crisis in Ukraine, threatening to impose fresh sanctions against Russia.Unelected World Health Organisation officials still proud to hold summit in Russia
Tobacco control industry professionals from around the world are looking forward to their sightseeing tour of Moscow in October. "Russia is a model tobacco control nation and not a basket case at all", says spokesperson.OK, I may have made the last one up.