EU President Herman Van Rompuy said the 28 leaders meeting in Brussels agreed to take "further significant steps" if Moscow did not back down.

The European Commission, the EU's executive arm, has been ordered to produce options for new sanctions within a week, he said.

"Everybody is fully aware that we have to act quickly given the evolution on the ground and the tragic loss of life of the last days," Van Rompuy told a news conference.

German Chancellor Angela Merkel also said the new sanctions would build on existing measures against Russia which mainly cover financial services, armaments and energy.

The sanctions plan came after Ukrainian President Petro Poroshenko visited Brussels to urge the EU to take tougher steps against Russia which he accused of military involvement in Ukraine.

Lithuania's President Dalia Grybauskaite, whose Baltic nation is wary of claimed Russia’s presence on its own borders, gave a similar warning as she urged the EU to send military equipment to Kiev.

The EU delivered a further riposte to Russia on Saturday when it appointed Polish Prime Minister Donald Tusk, a vocal Kremlin critic, to replace Van Rompuy as its next president.

The EU and the United States have already slapped tough sanctions on Russia for its alleged role in the Ukraine crisis, including Moscow's annexation of Crimea in March.

Moscow has strongly denied any troop presence in its western neighbor, and called all Ukraine-related scenario as a plot hatched by US and Western countries to strengthen NATO and Pentagon military presence in the region.

NATO has recently dropped a great deal of military equipment in Ukraine borders under pretext of confronting any probable aggression by Moscow.

The sudden reaction of EU countries came only days after the previous round of sanctions against Moscow seem to be totally ineffective.

NJF/NJF