Sofia, Bulgaria/Moscow NATO's top commander says new columns of Russian troops and tanks have rolled into eastern Ukraine, the claim promptly denied by Moscow.

US Gen. Philip Breedlove said Wednesday that in the last two days "we have seen columns of Russian equipment, primarily Russian tanks, Russian artillery, Russian air defense systems and Russian combat troops entering into Ukraine."

Breedlove, who spoke in Sofia, Bulgaria wouldn't say how many fresh troops and weapons have moved into Ukraine and wouldn't specify how the alliance obtained the information. The Russian Defense Ministry quickly rejected Breedlove's statement as groundless.

The West and Ukraine have continuously accused Moscow of fueling a pro-Russian insurgency in eastern Ukraine with troops and weapons the claims Russia has rejected.

Breedlove said the Russia-Ukraine border "is completely wide-open."

General-Major Igor Konashenkov, a Russian Defense Ministry official, dismissed the comments as anti-Russian "hot air" and said "there was and is no evidence" behind the NATO accusations.

"We have already stopped paying attention to unsubstantiated statements by NATO's Supreme Allied Commander Europe, General Philip Breedlove, on Russian military convoys he 'observed' allegedly invading Ukraine," Konashenkov said.

The West has imposed sanctions on Russia over the crisis in Ukraine, saying Moscow has provided the rebels with arms and reinforced them with troops since they rose up a month Russia annexed the Crimea peninsula from Ukraine in March.

Breedlove said in Bulgaria that NATO had seen "Russian equipment, primarily Russian tanks, Russian artillery, Russian air defense systems and Russian combat troops entering into Ukraine" in recent days.

Fighting has intensified around the rebel stronghold of Donetsk in east Ukraine, putting further pressure on a patchy ceasefire between rivals. Kiev says it is redeploying forces to prepare for a possible new rebel offensive.

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NATO says Russia sent more troops to Ukraine. Russians say NATO full of 'hot air' (+video)