Moscow: Russian President Vladimir Putin has cast Moscow's military action in Ukraine as a forced response to Western policies.

Speaking at a military parade on Monday marking the World War II victory over the Nazis, Putin drew parallels between the Red Army's fighting against Nazi troops and the Russian forces' action in Ukraine. He said that the campaign in Ukraine was a timely and necessary move to ward off a potential aggression.

He added that the Russian troops were fighting for the country's security in Ukraine and observed a minute of silence to honour the troops who fell in combat.

Impeccably straight columns of soldiers will march through Red Square on Monday as they do every year on Victory Day.

Tanks, armoured personnel carriers and transports carrying huge intercontinental ballistic missiles will rattle across the paving stones. But this year's observance of Russia's most important patriotic holiday carries exceptional weight.

The annual show in Red Square commemorating the defeat of Nazi Germany has become so ritualized that one year's parade is barely distinguishable from others.

A previously unseen piece of equipment might appear; the medal-festooned World War II veterans in the viewing stands become frailer and fewer in number each year. Its predictability can dilute its emotional power.

This year, as Russian troops fight gruelling battles in Ukraine and unleash torrents of missiles and bombs, few Russians are likely to be dulled by the parade's rituals. Instead, they will watch it for signs of what could come next in the conflict.

Some Russians fear President Vladimir Putin will use his speech at the parade to declare the special military operation in Ukraine - as the Kremlin insists it be called - as a full-fledged war.

That declaration would precede a broad mobilization of troops to bolster Russia's forces.

Asked by The Associated Press whether mobilization rumours could dampen the Victory Day mood, Putin spokesman Dmitry Peskov said nothing will cast a shadow over the sacred day, the most important day for Russians.

Human rights groups report a spike in calls from people asking about laws concerning mobilisation and their rights in case of being ordered to join the military.

Russian state TV has ramped up the patriotic rhetoric.

In announcing the February 24 military operation, Putin declared it was aimed at the demilitarization of Ukraine to remove a perceived military threat to Russia by neo-Nazis.

A recent TV commentary said Putin's words were not an abstract thing and not a slogan and praised Russia's success in Ukraine, even though Moscow's troops have gotten bogged down, making only minor gains in recent weeks.

One official has suggested that Victory Day marchers display photos of soldiers now fighting in Ukraine. Normally on the holiday, Russians carry portraits of their relatives who took part in World War II to honour those in the so-called Immortal Regiment from a conflict in which the Soviet Union lost a staggering 27 million people.