Ukraine’s armed forces on Sunday uploaded a video of what they said was a downed Russian jet crashing in flames in the eastern city of Kharkiv. Reuters has been unable to verify the claim. The location in the video matches that of buildings seen on satellite and street-level images of Kharkiv close to the city’s National Aerospace University. Russia has concentrated much of its firepower on the south and east of the country since its assault began on Feb. 24, besieging cities including Kharkiv and Mariupol with shelling and airstrikes, and causing extensive damage and casualties.