Russia on Thursday accused the United States of funding research into the development of biological weapons in Ukraine, as Moscow stepped up its campaign to gain control of key Ukrainian cities.

Russian defence ministry spokesman Igor Konashenkov said in a televised briefing that “the purpose of this — and other Pentagon-funded biological research in Ukraine — was to establish a mechanism for the stealthy spread of deadly pathogens.”

Konashenkov claimed the ministry had obtained documents detailing US military-biological activities in Ukraine, including on the transfer of Ukrainians’ biomaterial abroad.

He said Washington “planned to carry out research on a bird, bat, and reptile pathogens”, as well as on African swine fever and anthrax.

“Biolaboratories set up and funded in Ukraine have been experimenting with bat coronavirus samples,” Konashenkov added.

Both Washington and Kyiv have denied the existence of laboratories intended to produce biological weapons in the country, which has faced a Russian assault by tens of thousands of troops since February 24.

Russia in 2018 accused the United States of secretly carrying out biological experiments in a lab in Georgia, another former Soviet republic, which like Ukraine aims to join NATO and the European Union.