The United Kingdom has sent “thousands of rounds of Challenger 2 ammunition to Ukraine, including depleted uranium armor-piercing rounds,” Britain's armed forces minister James Heappy said on April 25 in response to a public inquiry on the U.K. Parliament’s website.

Heappy added that for security reasons, the British government would not comment on Ukrainian usage rates.

Russia's embassy in London responded by claiming that the U.K. "will not be able to evade responsibility for the consequences of the use of depleted uranium shells transferred to the Armed Forces of Ukraine," Russian state-controlled news outlet Tass reported on Telegram, citing the Russian embassy.

Earlier, on March 21, the U.K. confirmed that some of the ammunition the country would deliver to Ukraine alongside Challenger 2 tanks contained depleted uranium.

Following the announcement, Russian dictator Vladimir Putin threatened a response due to the weapons having a ‘nuclear component.’ Russia placed nuclear weapons on Belarus’ western border on April 2, allegedly in response to the U.K.’s decision to supply Ukraine with the ammunition.

The U.K. Defense Ministry responded by saying that depleted uranium is a standard component and has nothing to do with nuclear weapons or capabilities. “Russia knows this, but is deliberately trying to disinform,” it said at the time.

Depleted uranium is roughly two and a half times denser than steel, which makes it particularly effective for piercing heavy armor on the battlefield.