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

U.S. 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 defence 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 Defence 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."