President Vladimir Putin on Tuesday vowed Russia would be victorious in Ukraine during a military parade on Red Square and blamed Western countries for the conflict, comparing the fighting to World War II.

But his defiant address was overshadowed by scathing comments from Yevgeny Prigozhin, the head of Russian mercenary group Wagner, who accused Russia's military of repeated failures in Ukraine.

EU chief Ursula von der Leyen met Ukrainian President Volodymyr Zelensky to mark Europe Day that celebrates peace and unity, a symbolic retort to Moscow's Victory Day parade.

During his address, Putin told columns of military personnel in ceremonial uniform in Moscow that the country's future rests on Russian soldiers fighting in Ukraine.

"Today civilisation is again at a decisive turning point," Putin said standing shoulder to shoulder with elderly veterans and soldiers from Russia's Ukraine campaign.

"A war has been unleashed against our motherland," he said, adding that "the future of our statehood and our people depend on you."

"For Russia, for our armed forces, for victory! Hurrah!"

The anniversary of the Soviet Union's victory over Nazi Germany 78 years ago has been overshadowed by the military's slow gains and heavy losses in Ukraine.

- Wagner accusations -

In remarks released at the same time as Putin's speech, the head of Wagner accused a Russian unit of abandoning their positions near Bakhmut, the epicentre of the fighting in Ukraine.

"They all fled, exposing the front," Prigozhin said, repeating a vow that his men would leave Bakhmut by May 10 if the Russian military does not supply more ammunition.

Wagner has been leading Russia's months-long assault for Bakhmut, a destroyed industrial town in eastern Ukraine, where Russian forces have little to show after a winter offensive.

"Why is the state not able to defend its country?" Prigozhin said in a scathing video, in which he also accused Russian military top brass of trying to "deceive" Putin on how the Ukraine campaign was being led.

In the streets of Moscow, Russian families had come out to view the parade, which had tightened security.

Giya Merkeliya, a 55-year-old driver, carried a portrait of his grandfather, killed in 1943 during fighting in southern Russia.

"I'm waiting for victory," he said, and "for all our guys to come back, for everything to be okay," he told AFP journalists in Moscow.

Putin, despite being isolated on the world stage since launching the conflict in February 2022, was joined on Red Square by leaders of several ex-Soviet states, including Armenia and Kazakhstan.

- 'Geopolitical' -

But in Poland, Russia's ambassador was blocked by pro-Ukrainian activists from laying flowers at a Soviet memorial in the capital Warsaw.

German Chancellor Olaf Scholz told the European Parliament in Strasbourg that Russia's "show of force" in Moscow would not intimidate the European Union, which he said should reform to become a larger "geopolitical" bloc.

The EU should stay "steadfast in our support for Ukraine, as long as it is necessary", he said in Strasbourg, France.

In the run-up to Victory Day, Russia was hit with several acts of sabotage, including an explosion that derailed a train, a drone attack on the Kremlin and a car bomb that wounded a pro-Kremlin writer.

Kremlin spokesman Dmitry Peskov said that "all necessary measures" were being taken to ensure the safety of the leaders.

Still more than two dozen cities and towns cancelled plans to stage their own military parades over security concerns.

Since coming to power in 2000, Putin has stoked patriotic fervour around the 1945 Soviet victory over the Nazis, boosting his standing as the heir of Soviet power.

The Kremlin has also used the memory of the Soviet war effort to justify its offensive in Ukraine, claiming it is fighting "fascists" supported by the West.

- 'European family' -

The president of the European Commission meanwhile travelled by train from Poland to Kyiv to meet Zelensky and work on his country's quest for eventual EU membership.

"Ukraine is fighting for the ideals of Europe that we celebrate today. In Russia, Putin and his regime have destroyed these values. And now they are attempting to destroy them here in Ukraine," von der Leyen said.

Zelensky urged the EU to speed up deliveries of artillery shells, seen as key for an Ukrainian counteroffensive against Russian positions expected in the coming weeks.

"We discussed a key issue: the speed of procurement and delivery of these munitions. The need for them on the battlefield is already present," Zelensky said during a press conference in Kyiv.

And he said "the time has come" to make a decision on starting talks for Ukraine to join the European Union.

Zelensky earlier this week decreed that May 9 would be celebrated in his country as Europe Day, as it is in Brussels, spurning the martial Victory Day tradition of the former Soviet Union.

Shortly before von der Leyen arrived, Ukraine's air force said it had downed 23 out of 25 cruise missiles launched by Russia in the night between Monday and Tuesday.

The air alert in Kyiv ended about an hour before her arrival.