Russian Deputy Foreign Minister Sergei Ryabkov said on Thursday that the US supply of depleted uranium weapons to Ukraine was “a criminal act”, state media reported.

The Pentagon on Wednesday announced a new security assistance package worth up to $175 million for Ukraine, including depleted uranium ammunition for U.S. Abrams tanks.

A by-product of uranium enrichment, depleted uranium is used for ammunition because its extreme density gives rounds the ability to easily penetrate armor plating. Critics say there are dangerous health risks from ingesting or inhaling depleted uranium dust, including cancers and birth defects.