The European Union has given Russia one week to reverse course in Ukraine or face new sanctions.
European Council President Herman Van Rompuy said the EU was working urgently on further restrictive measures, according to the (BBC).
Earlier, Ukrainian President Petro Poroshenko said his country was “close to a point of no return – full scale-war” with Russia.
Russia denies Western accusations that its forces have illegally crossed into Ukraine to support separatists there.
Pro-Russian rebels have made gains against Ukrainian troops in recent days in the eastern Donetsk and Luhansk regions.
Some 2,600 people have died in fighting.
The conflict in the east erupted in April following Russia’s annexation of Ukraine’s southern Crimea peninsula a month before.