A United States-based satellite company has said that it has found a mass burial site with over 200 graves near the city of Mariupol in southeastern Ukraine, The Washington Post reported on Friday.

The city has been the site of conflict between Ukraine and Russia for several weeks. Russian forces now control most of Mariupol, according to the BBC.

The satellite company, Maxar Technologies, said that its images showed multiple rows of graves in four separate sections, with each section measuring close to 280 feet. New graves at the site appeared between March 23 and March 26, according to the company.

The alleged mass graves are said to have been located near a village named Manhush, about 20 kilometres to the west of Mariupol. Russia has not yet responded to the allegations.

The Mariupol City Council, in a message on Telegram, said that up to 9,000 civilians may have been buried in the mass graves. The authority claimed to have information that the bodies were buried in several layers.

The city mayor Vadym Boichenko described the site as a “new Babyn Yar”, in a reference to a large mass grave near the Ukrainian capital of Kyiv, where over 30,000 Jews were said to have been killed by Nazi forces.

“The biggest war crime of the 21st century was committed in Mariupol,” he said, according to The Washington Post. “This is the new Babyn Yar...We need to do everything we can to stop the genocide.”

The city council provided its own aerial imagery of the site and claimed that it was “twice as large as the nearby cemetery”.

On Thursday, Russian President Vladimir Putin claimed that Russian forces had “liberated” Mariupol, and said that it was biggest battle in the conflict, according to Reuters.

Putin said that it was not necessary to attack an industrial zone that has the Azovstal steel plant. “There’s no need to climb into these catacombs and crawl underground through these industrial facilities,” he said. “Block off this industrial area so that not even a fly can get through.”

However, the United States disputed Russia’s claim saying that it believes Ukraine is still holding ground in the city.