Russian President Vladimir Putin has blamed Moscow's invasion of Ukraine on western policies and said it was necessary to ward off potential aggression.

Speaking at a military parade in Red Square to mark the Second World War victory over Nazi Germany, Mr Putin drew parallels between the Red Army's fighting against the Nazi troops and the Russian forces' action in Ukraine.

While lambasting the West, Mr Putin gave no indication of a shift in strategies or made any indication he is going to declare a broad mobilisation, as some in Ukraine and the West fear.

Addressing the phalanxes of elite Russian troops filling Red Square, Mr Putin said the campaign in Ukraine was needed to avert "a threat that was absolutely unacceptable to us (that) has been methodically created next to our borders".

"The danger was rising by the day," he claimed, adding "Russia has given a pre-emptive response to an aggression" in a "forced, timely and the only correct decision by a sovereign, powerful and independent country".

The Russian leader has repeatedly accused Ukraine of harbouring aggressive intentions with support from the US and its allies - claims Ukrainian and western officials have denied.

In his speech at the parade, Mr Putin again scolded the West for failing to heed Russian demands for security guarantees and a roll-back to Nato's expansion, arguing it left Moscow no other choice but to attack Ukraine.

The Russian leader said Russian troops in Ukraine are fighting for the country's security and called a minute of silence to honour the soldiers killed combat.

Mr Putin said some of the troops taking part in the parade have previously fought in Ukraine.

He said the troops in Ukraine have been "fighting for the Motherland so that no one will forget the lessons of World War Two and there will be no place in the world for hangmen, executioners and the Nazis".

The Victory Day that Russia marks on May 9 is the country's most important holiday, celebrated with military parades and fireworks across the county.

The Soviet Union lost 27 million people in the Second World War, which it calls the Great Patriotic War.

The conflict, which devastated the country and caused enormous suffering, has left a deep scar in the national psyche.

Some in Ukraine and the West expected Mr Putin to use his speech at the parade to switch from calling the attack on Ukraine a "special military operation" to acknowledging it as a war.

Mr Putin did not make any such shift in rhetoric or give any indication that the Kremlin may change its strategy and declare a broad mobilisation to beef up its ranks.

The Kremlin has focussed on Ukraine's eastern industrial heartland known as the Donbas, where Moscow-backed rebels have been fighting Ukrainian government forces since 2014.

That conflict erupted weeks after Russia's annexation of Ukraine's Crimean Peninsula.

The Russian military has re-armed and re-supplied its forces withdrawn from areas near Kyiv and other regions in Ukraine's north-east and moved them to Donbas in an apparent attempt to encircle and destroy the most capable and seasoned Ukrainian troops concentrated there.