Ukraine's interim government has accused Russia of orchestrating unrest in the country, after gunmen seized several further government buildings in eastern Ukraine.
It comes just days after government buildings in Donetsk were seized by protesters in the majority Russian-speaking east of the country, who are demanding a union with Russia.
On Saturday, pro-Russian militiamen stormed a security services headquarters and a police station in the town of Sloviansk, and other seizures of government buildings were reported in Druzhkovka.
A regional police spokesman said armed men were bussed to the town's police station.
"Six or seven unknown persons got out. They fired several shots in the air and attempted to storm the police department," he said, according to the BBC.
Responding to the fresh violence, Ukrainian interim Foreign Minister Andrei Deshchytsia called on the Kremlin to end "provocative" actions by its agents.
Ukrainian officials have previously accused Russian military and intelligence officials of direct participation in unrest in the Crimea, which Russia formally annexed last month.
For its part, Russia has denied any involvement in the unrest. But Ukraine and western government alike have expressed concern over the 40,000 Russian troops amassed along near the Ukrainian border, raising concerns of another de facto military invasion in Ukraine - particularly amid calls by some pro-Russian protesters for Moscow to do just that.
But Russia's Foreign Ministry insisted Wednesday that there is "no reason for concern" about the presence of Russian forces, which it claims are merely in the midst of training exercises.
"Russia has repeatedly stated that it does not conduct unusual or unplanned activities which are militarily significant on its territory near the border with Ukraine," the Foreign Ministry said, calling accusations of a planned attack "groundless."
Calling for NATO help
Meanwhile, Russia and Ukraine's jittery Eastern European neighbors have urged NATO to provide ground troops and other forms of military support as a means of deterring Russia from seizing territory in regions with Russian-speaking majorities.
Estonia, Latvia, Lithuania, Poland and Romania have all turned to the western alliance in moves which hark back to the Cold War era.
Estonian Defense Minister Sven Mikser is set to meet NATO chief Fogh Rasmussen in Brussels on Monday, and said talks were already underway "about having NATO rotating land units in our region", according to AFP.
Lithuanian Defense Minister Juozas Olekas said a NATO presence in his country "could take various forms - from instructors to permanently deployed land, naval, special operation or air forces."
And Poland's opposition leader has suggested that only installing US military bases in his country would deter Moscow's “expansionist ambitions”.