Ukrainian interior minister Arsen Avakov has revealed that three tanks have crossed the Ukrainian border from Russia as fighting resumed in the country's east.
"Tonight, three T-72 tanks crossed Ukraine's state border from Russia. One tank is in the town of Snizhne," he said.
"Two other tanks moved out of the town. In the vicinity of Snizhne these tanks were intercepted by Ukrainian troops. The fight is ongoing. There are reports that a Russian T-72 was hit."
He said that the Russian tanks entered Ukraine at a checkpoint controlled by pro-Russian separatists in the Dyakove area in the eastern Luhansk region.
They proceeded to move into the troubled Donetsk region with armoured troop carriers. They reached the town of Snizhne before two others moved to Horlivka town where the Ukrainian forces engaged the tanks.
Pro-Russian separatists are yet to confirm reports of Russian tanks entering through their Luhansk checkpoint.
However, unverified footage has been uploaded of a Russian tank moving through Snizhne town.
Russia is to submit a draft resolution to the UN Security Council for Ukraine to impose a "road map" to peace after Kiev failed to end unrest in the country's east, according to Russian Foreign Minister Sergei Lavrov.
"We have assigned our (U.N.) envoy in New York, Vitaly Churkin, to submit a draft resolution to the Security Council on the situation in Ukraine," state news agency Itar-Tass quoted Lavrov as saying.
"That is because the lack of any progress in the efforts to end the violence ... is causing growing concern," he continued.
Separatists in the regions of Donetsk and Luhansk declared independence after holding separate referendums last month. Both were declared illegal by Kiev and their western allies.