Russia's Defense Ministry has denied that it shot down a Ukrainian fighter jet and called the accusation by Kyiv "absurd."
A spokesman for Ukraine's National Defense and Security Council, Andriy Lysenko, said the Ukrainian SU-25 fighter was brought down on the evening of July 16 "as it fulfilled its task over the territory of Ukraine."
Lysenko said the pilot was able to eject from the plane and was evacuated safely. Ukraine's military said the plane was brought down about 15 kilometers from the border with Russia.
A Russian Defense Ministry spokesman said the claim "is absurd, just like all the previous accusations from Kyiv's leadership" against Russia's military.
Ukrainian officials have recently accused Russia's armed forces of direct involvement in the three-and-a-half month conflict in which the pro-Western government in Kyiv is fighting to crush an armed rebellion by pro-Russian separatists in eastern Ukraine.
Earlier this week, Kyiv said a Ukrainian military transport plane downed on July 14 was "likely" hit by a missile fired from the Russian side of the border.
The Russian Defense Ministry spokesman said that despite claiming it had "irrefutable proof," Kyiv has so far failed to present any evidence of Russian involvement.
Lysenko also said on July 17 that Ukrainian forces stationed along the border were regularly subjected to artillery fire from Russian territory.
He also claimed there was growing evidence that regular Russian soldiers, wearing unmarked uniforms, are on Ukrainian territory.
Lysenko said five Ukrainian servicemen had been killed in the past 24 hours.
This would bring to more than 270 the number of servicemen killed since the government launched what it describes as an "antiterrorist" operation against the separatists.
Hundreds of civilians and rebels have also been reported killed.