Russia on Tuesday denied as "absolute nonsense" the latest accusations by Kiev that Moscow had sent hundreds of troops over the border into Ukraine.

"Yesterday's accusations from Kiev of the alleged deployment of Russian army contingents across the Russian-Ukrainian border do not stand up to any criticism," Defense Ministry spokesman Igor Konashenkov said, Russian news agencies reported.

"It is absolute nonsense," Konashenkov added, further describing the latest allegations from Ukraine as a "hallucination".

Kiev on Monday accused Russia of sending some 700 reinforcements to bolster separatist fighters battling Ukrainian forces around the rebel bastion of Donetsk.

Ukraine security spokesman Andriy Lysenko said on Monday that "two groups of armed forces from the Russian Federation crossed the border" into rebel-held territory.

Russia has repeatedly denied previous accusations from Kiev and its allies in the West that it has sent troops and weapons to back up the rebels.

At least three civilians were killed in shelling Tuesday in eastern Ukraine as fighting continued between government and rebel forces in the separatist-held city of Donetsk.

AFP - AP