The Russian defence manufacturing sector is likely turning to prison labour to try to meet wartime production demands, the Ministry of Defence (MOD) says.
Russia's largest tank manufacturer, Uralvagonzavod, told reporters it would employ 250 prisoners after consulting the Federal Penal Service, the MOD added.
Forced labour as a criminal punishment was reintroduced to Russia in 2017.
- Fate of Ukrainian town Soledar hangs in the balance amid brutal battle
- Challenger 2: The British tank that's never been destroyed in battle
- Poland to send Leopard tanks to Ukraine as part of wider coalition
It comes as willing volunteers for Russia's 'special military operation' in Ukraine are in short supply, according to UK defence intelligence.
The fate of Soledar in eastern Ukraine hangs in the balance amid one of the fiercest battles of Russia's invasion.
Russian forces have used jets, mortars and rockets to bombard the devastated salt-mining town in an unrelenting assault.
Ukraine's unflagging resistance and other challenges have prompted Moscow to shake up its military leadership again.
Meanwhile, British Challenger 2 main battle tanks could be heading to Ukraine to help its defence.
Poland has agreed to send German-made Leopard 2 tanks to Ukraine as part of a larger international coalition.
Polish President Andrzej Duda made the announcement after a meeting in Lviv with Ukrainian President Volodymyr Zelensky, who said his country needs tanks to win the war.