Russian military leaders claim their forces took over the salt-mining town of Soledar.

Video showed Russian soldiers evacuating civilians from Soledar and nearby villages to the city of Shakhtarsk as fighting took place on the outskirts on Friday.

Serhiy Cherevaty, the Ukrainian commander of the Eastern Group of Forces, however, confirmed that fighting was going on in the region but contested Russia's claims about the status of the city in a statement to ABC News.

"We have a clear understanding of who controls which streets in the city, but I cannot reveal those details," he told ABC News.

-ABC News' Ellie Kaufman and Patrick Reevell

Pressure is mounting for key NATO allies to send tanks to Ukraine.

After meeting with Ukrainian President Volodymyr Zelenskyy on Wednesday, Polish President Andrzej Duda said his country plans to supply Leopard tanks to Ukraine but only as part of an "international coalition."

"They will be provided within the coalition, because you know that it is necessary to obtain certain official consents. But first we need to build an international coalition and we have decided to form this international coalition," Duda said.

Duda “expressed hope” other NATO countries would provide Ukraine with tanks as well.

The United Kingdom has not made a final decision on whether to send tanks to Ukraine, according to the spokesperson for British Prime Minister Rishi Sunak. The United Kingdom is considering supplying Ukraine with the British Army’s Challenger 2 main battle tank, according to British media reports.

Germany is also facing pressure from Ukraine and other NATO allies to send tanks to Ukraine. So far, they have not committed to sending any tanks to the country and neither has the United States.

Germany and the United States have both agreed to supply Ukraine with armored carriers and the Patriot air defense system.

Russian and Ukrainian officials offered conflicting views Thursday on the battle being waged over the eastern Ukraine city of Soledar.

Both sides described their forces as making progress in the fight for the salt mining town in the Donbas region.

"Our defenders continue to hold their positions on the most difficult frontlines and in the battle for (the) Donbas," said Hanna Maliar, the Ukrainian deputy of defense. "Today, fierce and heavy battles continue in the direction of Bakhmut, in the area of Soledar city."

Despite the "difficult situation," Ukrainian soldiers are desperately battling for control of Soledar, Maliar said.

"The enemy is suffering heavy losses, unsuccessfully trying to break through our defenses and capture Soledar," Maliar said. "Today, the city's approaches are literally littered with the bodies of Putin's destroyed troops. Nevertheless, they move over the bodies of their fallen fighters. Our defenders show maximum resilience and heroism."

But Kremlin spokesperson Dmitry Peskov said Thursday that Russian forces and mercenaries from the Wagner private military company are doing a "truly colossal job" in Soledar.

"These are absolutely selfless, heroic deeds," Peskov told journalists on Thursday.

Peskov said the hostilities in the region will continue.

"There is still a lot of work to be done. No time to stop, no time to rub our hands and so on. The main work is yet to come," Peskov said.

The Russian Defense Ministry said on Wednesday that Russia's airborne units had blocked Soledar from the north and the south and assault teams were fighting within the town limits.

Ukrainian President Volodymyr Zelenskyy said in his daily address on Wednesday that Ukrainian troops are holding onto Soledar.

"The terrorist state and its propagandists are trying to pretend" to have achieved some successes in Soledar, Zelenskyy said. "But the fighting continues."

Russia has replaced the military chief in charge in Ukraine, according to the Kremlin.

Army Gen. Valery Gerasimov, chief of the general staff of the Russian armed forces, will replace Sergei Surovikin, who has been commander of Russia's forces in Ukraine for the past three months. Surovikin will become one of Gerasimov's deputies, according to Sergei Shoigu, Russia's minister of defense, who made the new appointments.

The changes come as the progress of the Russian forces in Ukraine continues to stall.

"The increase in the level of leadership of the special operation is linked to the expansion of the scale of the tasks at hand and the need to organize closer interaction between troops," Shoigu said.

U.S. President Joe Biden made an unannounced visit to war-torn Ukraine on Monday, arriving in Kyiv as Washington signals its ongoing support ahead of the one-year anniversary of Russia's invasion.

Biden's visit came ahead of a planned meeting with NATO allies in Poland. He is expected to give a speech at the Royal Castle Arcades in Warsaw on Tuesday evening to offer an appraisal of international support during the first year of the war and to address "how we will continue to stand with the people of Ukraine for as long as it takes," White House spokesperson Karine Jean-Pierre said in a statement earlier this month.

Biden also plans to meet in Poland with leaders of the Bucharest Nine, a group of eastern NATO allies formed in 2015 in response to Russia's annexation of Ukraine's Crimean Peninsula.

Ukrainian President Volodymyr Zelenskyy made a dramatic visit to the United States in December, his first known international trip since the Russian invasion began in February 2022. Zelenskyy met with Biden at the White House in Washington, D.C., before addressing members of U.S. Congress on Capitol Hill.