STORY: A GoPro camera mounted on a Ukrainian tank shows the vehicle crawling forward. Its massive canon then lobs shells downrange.This video, released by the Ukrainian military, claims to show fighting near the shattered city of Bakhmut in the eastern part of the country, where Kyiv's soldiers have fought Russian invaders for months in a battle both sides have described as a "meat grinder," but neither has so far managed to win.The tank's platoon commander, call-sign "Bender," told Reuters his unit fired on Russian positions, in support of Ukrainian infantry.Russia has claimed in recent days to have made progress in street-by-street fighting. British intelligence on Wednesday said Ukrainian forces had successfully pushed the Russians back from one of the city's main supply routes.The head of a private Russian mercenary group heavily involved in the Bakhmut operation on Wednesday acknowledged that the fighting had badly damaged his forces."The enemies of democracy must lose."Speaking to a summit of democracies sponsored by U.S. President Joe Biden on Wednesday, Ukrainian President Volodymyr Zelenskiy told fellow leaders that they needed to hold firm in the face of Russian aggression.He again pleaded for continued arms and support to help his forces push back Moscow. Ukraine has in recent months begun to receive a suite of modern military hardware promised by the U.S. and NATO to help Kyiv mount an expected spring counter-offensive.It's unclear where and when that operation might take place.Ukraine on Wednesday struck a railway depot and knocked out power in the Russian-occupied city of Melitopol, but Kyiv hasn't said what weapons it might have used. The city just at the edge of the range of American-provided HIMARS rocket-launchers, and within range of newer American armaments.Melitopol is a rail hub and administrative center of the Russian-controlled Zaporizhzhia region.It's south of the Russian-held Zaporizhzhia nuclear power plant, visited on Wednesday by U.N. nuclear agency chief Rafael Grossi."It is very very important that we agree on the fundamental principle that the nuclear power plant should not be attacked."Grossi has been pushing for a safety agreement between Ukraine and Russia to protect the facility.Moscow and Kyiv have repeatedly accused each other of shelling the site of the power station over the last year.The sprawling Zaporizhzhia nuclear plant was a prized part of Ukraine's energy network and accounted for around 20% of national power generation before the Russian invasion.It has not produced any electricity since September, when the last of its six reactors was taken offline.