Local residents sit on a bench near an apartment building destroyed in the course of Ukraine-Russia conflict in the besieged southern port city of Mariupol, Ukraine. File/Reuters

Russia on Thursday marked the Soviet Union's victory over Nazi Germany in World War Two as relations with the West spiral deeper into crisis over the advance of Russian troops against Ukraine's Western-backed forces.

Vladimir Putin, who rose to power just eight years after the Soviet Union broke up, will speak at the Victory Day parade on Red Square though there will be less military hardware on display than in parades before Russia's 2022 invasion of Ukraine.

Putin now casts the war as part of a holy struggle with the West, which he says has forgotten the role played by the Soviet Union in defeating Nazi Germany and the lesson that neither Napoleon Bonaparte nor Adolf Hitler could defeat Russia.

"I want to bow to our heroes, the participants of the special military operation, to all those who are fighting for the Fatherland," Putin said as he was sworn in for a new term as president on Tuesday.

The 71-year-old Kremlin chief promised victory in the war, where Russian forces have been advancing against Ukrainian forces despite hundreds of billions of dollars in aid from the United States and its allies.

Ukraine and the West say Putin is engaged in an imperial-style land grab and have vowed to defeat Russia, which currently controls about 18% of Ukraine, including Crimea, and parts of four regions in eastern Ukraine. Russia says the lands, once part of the Russian Empire, are now again part of Russia.

War?

The Soviet Union lost 27 million people in World War Two, including many millions in Ukraine, but eventually pushed Nazi forces back to Berlin, where Hitler committed suicide and the red Soviet Victory Banner was raised over the Reichstag in 1945.

Vladimir Putin

Nazi Germany's unconditional surrender came into force at 11:01 p.m. on May 8, 1945, marked as "Victory in Europe Day" by France, Britain and the United States. In Moscow it was already May 9, which became the Soviet Union's "Victory Day" in what Russians call the Great Patriotic War of 1941-45.

Parades took place in major cities across Russia's 11 timezones. The Moscow parade will begin at 0700 GMT, though Russian media reported there would be less military hardware than in the pre-Ukraine war years.

Unlike some of the parades of the past, there will be no leaders from the West. Russia said ambassadors of "unfriendly" countries - broadly the West and those who support Ukraine - had not been invited to the parade.

Present will be the leaders of Belarus, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, Cuba, Laos and Guinea-Bissau. In Ukraine, Russian missiles struck infrastructure overnight and there were several drone attacks on Russian territory.

Neither Russia nor Ukraine publish reliable data on the number of men they have lost in the war, though Western intelligence estimates put the total number of killed and wounded in the hundreds of thousands.

Russian officials warn that the Ukraine war is entering the most dangerous phase to date - Putin has repeatedly warned of the risk of a much broader war involving the world's biggest nuclear powers.

The crisis has deepened in recent weeks: U.S. President Joe Biden signed off on $61 billion in aid to Ukraine; Britain said that Ukraine had the right to strike Russia with British weapons; and French President Emmanuel Macron has refused to rule out sending French troops to fight Russian forces.