Tanks, missiles part of Red Square parade in Moscow

Victory Day, marking the defeat of Nazi Germany, is Russia's most important secular holiday -a time both to honor the enormous sacrifices of World War II and to assert the country's military strength.

Russia in recent years has nearly quadrupled its defense spending, aiming to resuscitate the military forces that deteriorated severely in the post-Soviet period.

Showing the heavy weaponry underlines the military revival, but also has raised concern that Russia has aggressive ambitions.

But President Dmitry Medvedev, in a speech opening the parade, warned against igniting conflicts and said the weaponry is for "the reliable defense of the homeland."