Russian border guards on Friday denied reports that a column of Russian armored personnel carriers (APCs) had rolled into eastern Ukraine.
Russian APCs actually operate on the Ukrainian border, where they form part of mobile units deployed to protect Russian citizens from hostilities in eastern Ukraine, a spokesman for the border guard service said in comments carried by the Interfax news agency.
The mobile groups never cross into Ukrainian territory, the spokesman added. The border guards form part of the Federal Security Service (FSB).
Two British reporters late Thursday saw 23 Russian APCs separate from a larger Ukraine-bound humanitarian convoy and roll into Ukraine, Guardian correspondent Shaun Walker said in a Twitter post.
The convoy of 262 trucks was dispatched by the Kremlin and is carrying humanitarian aid to Ukraine's Donetsk and Luhansk regions, which are in the grips of a pro-Russian insurgency.
Kiev was reluctant to let the convoy in, saying it could be pretext for a direct military invasion or carry military supplies for the separatists.
Ukrainian officials accuse Russia of backing the rebels, including by shelling of Ukrainian forces from Russian territory. Moscow has denied all claims.
Kiev eventually agreed to let the convoy in, provided the International Red Cross would be in charge of delivering the aid in Ukraine.
The convoy was undergoing customs inspection on the border as of Friday afternoon.