Russia's Defense Ministry denied on Thursday it had shot down a Ukrainian military jet and called the accusation by Kyiv “absurd,” Russian state news agency RIA reported.
“It is absurd, just like all the previous accusations from Kyiv's leadership against Russia's Defense Ministry,” a ministry spokesman was quoted as saying.
In the latest escalation of tensions on the Ukrainian-Russian border, Kyiv said a Russian jet shot down one of its warplanes, one of its strongest accusation yet of direct Russian military involvement in the conflict between pro-Russian rebels and Ukrainian forces in Ukraine's east.
A Ukrainian military spokesman said the pilot of the SU-25 fighter ejected safely.
NATO said, if confimed, the incident would represent a serious escalation.
"We have no confirmation of this. If confirmed. it would represent a grave further escalation and another direct violation by Russia of Ukraine’s territorial integrity and sovereignty," a NATO military officer, speaking on condition of anonymity, told VOA.
Ukraine's National Security and Defense Council (NSDC) on Thursday said a Russian air force plane downed the Ukrainian jet late Wednesday over Ukrainian territory with an air-to-air missile strike.
On the ground in eastern Ukraine, fierce fighting between government forces and pro-Moscow rebels has intensified in recent days with some 55 civilians killed since the weekend alone.
In what would represent an addititional escalation, NSDC spokesman Andriy Lysenko said Ukrainian troops had been fired upon by missiles from a village just inside Russia.
Ukrainian media have been circulating videos purportedly shot by residents of the Russia village of Gukovo showing rockets being launched from there allegedly toward Ukrainian territory.
The authenticity of the videos cannot be independently confirmed but one of them was tweeted by NATO Supreme Allied Commander Europe Gen. Philip Breedlove, who expressed deep concern.
I am deeply concerned by this latest video that appears to show Russia engaging in military action against Ukraine http://t.co/wqxtvzswZT— Phil Breedlove (@PMBreedlove) July 17, 2014
Officials in Kyiv have recently accused Russia's armed forces of being directly implicated in attacks on Ukrainian troops battling an insurgency near the border.
NATO has said it has evidence that Russia has moved over 12,000 troops back to its border region with Ukraine in recent weeks and that it continues to allow mercenaries and heavy weapons to flow across its borders into Ukraine.
Moscow denies Western charges that is sending fighters, supporting the separatists in Ukraine or fomenting the unrest there by any other means.
On Monday, Ukraine said one of its military transport planes carrying eight people was shot down by a missile fired from Russian territory.
Ukraine's Security Service chief Valentyn Nalyvaichenko said he had “unconditional evidence” that Russia was involved in downing the craft.
Rebels claimed to have shot that plane down.
VOA's Jeff Seldin contributed to this report. Some information provided by Reuters, AP and AFP.