Nearly 100 metres (330 feet) high and crowned by six golden domes, the Cathedral of the Armed Forces in a military theme park outside Moscow is now Russia's third-largest Orthodox Christian church.

It sparked controversy earlier this year when it was revealed that it would include mosaics featuring Putin and Soviet-era dictator Joseph Stalin. The mosaics were eventually removed at Putin's request.

"For us Russians, the memory of all those who fought, those who died, who with their strength brought us closer to victory in the Great Patriotic War, is sacred," Putin said in a televised ceremony, using the Russian name for the war.

"We are improving the armed forces, we are equipping them with new material, their combat capacity is increasing," Putin said alongside the head of the Russian Orthodox Church, Patriarch Kirill.

The ceremony was held on the 79th anniversary of the Nazi invasion of the Soviet Union and ahead of a huge military parade planned on Wednesday to mark 75 years since victory in the war.

Putin was forced to reschedule the parade from May 9 because of the coronavirus pandemic, which has seen Russia record the world's third-highest number of cases.

He has also rescheduled a public vote on constitutional reforms, initially planned for April, for July 1. Among other changes, the reforms will reset presidential term limits, allowing Putin to potentially stay in the Kremlin until 2036.

In power for 20 years, Putin often vaunts the country's military power and Orthodox Christian values to boost his support among Russians.