Russia says images of its military hardware at the Ukrainian border are from last year, and accuses Nato of using the Ukraine crisis to "rally the troops."
On Wednesday, Nato's top military commander in Europe, General Philip Breedlove, said the Russian military presence at the border continues - and released satellite images of tanks, attack helicopters and war planes.
Today, according to the state-run newsagency RIA, an official in the Russian military general staff said the satellite shots were taken in August 2013.
According to General Breedlove, countermoves to the Russian military threat against Ukraine could include sending American troops to alliance nations in eastern Europe feeling at risk.
If Russia is serious about a dialogue, the first step should be to pull back its troops Nato Secretary General Anders Fogh Rasmussen
But the Russian foreign ministry has said Nato's comments have been a bid to boost the appeal of the alliance.
"The constant accusations against us by the secretary general convince us that the alliance is trying to use the crisis in Ukraine to rally its ranks in the face of an imaginary external threat to Nato members and to strengthen demand for the alliance ... in the 21st century," a statement said.
More from Channel 4 News: Before/after: Nato 'proves' Russia build-up pics are genuine
Russia has denied that it has any plans to invade Ukraine.
Speaking in Prague on Thursday, Nato Secretary General Anders Fogh Rasmussen said: "I have this message to Russia: you have a choice to stop blaming others for your own actions, to stop massing your troops, to stop escalating this crisis and start engaging in a genuine dialogue." He added: "If Russia is serious about a dialogue, the first step should be to pull back its troops."
Russian Foreign Minister Sergei Lavrov was reported by the newsagency Interfax to have warned on Thursday that a deployment of Nato troops in regions bordering Russia would violate a previous agreement between Nato and Russia.
The images released by General Breedlove are said by Nato to have been taken on 22 March, nearly a month after the unrest in Crimea began that led to Russia's annexation of the area. The photographs were taken by commercial satellite imaging company Digital Globe.
You can see the images below.
Above: Purported to be Russian military Su-27/30 "Flankers" aircraft at the Primorko-Akhtarsk Air Base in southern Russia, on the Sea of Azov which borders Ukraine. (Image: Digital Globe).
Above: purported to be Russian military tanks and infantry fighting vehicles at a military base near Kuzminka, east of the Sea of Azov in southern Russia (picture: Digital Glob)
Above: purported to be a Russian military airborne or Spetznaz (special forces) brigade at Yeysk, near the Sea of Azov in southern Russia (picture: Digital Globe).
Above: purported to be a Russian artillery battalion at a military base near Novocherkassk, east of the Sea of Azov in southern Russia (picture: Digital Globe).
Above: purported to be Russian Mil Mi-8 "Hips" and Mil Mi-24 "Hinds" aircraft in Belgorod, north of the Russian border with eastern Ukraine (picture: Digital Globe).
Meanwhile, Ukraine's interior minister has warned pro-Russian protesters who have seized regional government buildings in eastern Uktrainian cities that a political solution is needed, or they will face "force".
Arsen Avakov, said that "either way, the stituation will be resolved in 48 hours".
Kiev has already conducted an "anti-terrorist" campaign against pro-Russian protesters in Kharkiv, and 70 "separatists" who seized a regional government administrative building have been arrested. Protesters in the city of Donetsk have declared independence from Kiev.