Putin addressed a vast parade on Red Square in Moscow for a public holiday celebrating Soviet victory in World War II, as the Russian armed forces have suffered major losses in Ukraine.

UK Defence Secretary Ben Wallace, himself a former soldier, was due to give a speech at the National Army Museum later Monday.

"All professional soldiers should be appalled at the behaviour of the Russian Army," he will say, according to excerpts released in advance by his department.

"Not only are they engaged in an illegal invasion and war crimes but their top brass have failed their own rank and file to the extent they should be court martialled."

Putin on Monday gave a speech to troops telling them they are defending the "Motherland" in Ukraine.

He has justified Russia's military actions by saying they are carrying out "denazification" of the neighbouring country.

Wallace said he wanted to "call out the absurdity of Russian generals -- resplendent in their manicured parade uniforms and weighed down by their many medals", saying they were "utterly complicit in Putin's hijacking of their forebears' proud history of... repelling fascism".

Ukrainian President Volodymyr Zelensky on Monday spoke of his pride in Ukrainians who fought to defeat Nazism, saying he would not allow victory in World War II to be "appropriated" by Russians.