Putin Could Use Chemical, Biological Weapons in Ukraine: Biden

Amid the devastation caused by Russia's unceasing bombardment of Ukrainian cities, President Volodymyr Zelensky highlighted the death of a 96-year-old survivor of Nazi concentration camps, killed in his flat by shelling in Kharkiv.

Nearly four weeks into their invasion, Russian troops have failed to capture any major Ukrainian city and have been halted on nearly all fronts, but are hammering residential districts with artillery, missiles and air strikes.

Russian forces were expected to continue to attack critical infrastructure with "high-precision weapons and indiscriminate munitions”, Ukraine's armed forces said in a statement.

Russia has been saying in recent weeks that Ukraine might possess chemical or biological weapons. Biden said those accusations were not merely false, but a sign that President Vladimir Putin might be planning to use such weapons himself.

"Now he's talking about new false flags he's setting up including, asserting that we in America have biological as well as chemical weapons in Europe, simply not true," Biden said at a business event on Monday. "They are also suggesting that Ukraine has biological and chemical weapons in Ukraine. That's a clear sign he's considering using both of those."

Putin calls the war, the biggest attack on a European state since World War Two, a "special military operation" to disarm Ukraine and protect it from "Nazis". The West calls that a false pretext for an unprovoked war of aggression.

In an address overnight, Zelensky drew attention to the death of Boris Romanchenko, a Holocaust survivor killed when his flat in besieged Kharkiv was shelled last week.

"Please think about how many things he has come through," said Zelensky. "But (he) was killed by a Russian strike, which hit an ordinary Kharkiv multi-storey building. With each day of this war, it becomes more obvious what 'denazification' means to them."

A memorial for the survivors of the Nazi concentration camp at Buchenwald said Romanchenko had served for many years as a vice president of the Buchenwald-Dora International Committee, devoting himself to documenting Nazi crimes. He had survived the Buchenwald, Dora-Mittelbau and Bergen-Belsen concentration camps in Germany during World War Two.

"We mourn the loss of a close friend," the memorial said.

In killing him, "Putin managed to 'accomplish' what even Hitler couldn't," Ukraine's Defence Ministry said on Twitter.