Sergey Leonov, a member of Russia’s State Duma, has proposed to forcibly take the blood of Ukrainian prisoners of war (POW) to treat injured civilians and Russian soldiers, Euromaidan Press reported late Wednesday.

"Naturally, we are talking about reasonable donations, and only for those whose health allows it,” the news website quoted the lawmaker.

Russia's nearly eight-week invasion has failed to capture any of Ukraine's largest cities.

Moscow was forced to retreat from northern Ukraine after an assault on Kyiv was repelled last month but has poured troops back in for an assault on the east that began this week.

The biggest attack on a European state since 1945 has led to nearly 5 million people fleeing abroad and reduced cities to rubble.

In the ruins of Mariupol, the site of the war's heaviest fighting and worst humanitarian catastrophe, Russia was hitting the last main Ukrainian stronghold, the Azovstal steel plant, with bunker-buster bombs, Kyiv said.

Ukraine says hundreds of civilians are sheltering beneath the factory.