A man holds a portrait of the Soviet dictator Josef Stalin against an Orthodox cathedral at the memorial built to honour those who died in the Battle of Stalingrad during the World War II, in the Russian city of Volgograd, formerly Stalingrad, on February 2, 2013

The city of Volgograd was renamed Stalingrad for a day on Saturday as Russia marked the 70th anniversary of a brutal battle in which the Red Army defeated Nazi forces and changed the course of World War II.

President Vladimir Putin called the battle "one of the greatest examples of world heroism" during a stirring address to Volgograd veterans that played up the nationalist themes of his third Kremlin term.

"Stalingrad will forever remain the symbol of the unity and invincibility of our people," said Putin.

"It is a symbol of true patriotism -- a symbol of the great victory of the Soviet soldier-liberator."

Commuter buses emblazoned with pictures of the feared Soviet dictator Joseph Stalin ran across the southern city as patriotic Russians honoured what many view as the Soviet people's greatest achievement.

"I remember the sadness of the war and the victory of the Soviet soldiers," said World War II veteran Alexander Kudlyayev as he joined 10,000 others at a wreath-laying ceremony at Volgograd's Tomb of the Unknown Soldier.

"I came to honour my friends who died here," added 89-year-old Stalingrad survivor Pyotr Chabarov.

The half-year battle in 1943 in the city on the Volga River -- much of it fought in hand-to-hand combat across the ruined streets -- claimed the lives of two million people on both sides and eventually led to the surrender of the German troops.

The battle marked Hitler's first big defeat and led to a Nazi retreat from Soviet territory after a lightning June 1941 invasion that had caught Stalin completely unaware.

The pulverised city was renamed Volgograd in 1961 after Soviet leaders admitted the extent of Stalin's tyranny during his decades in power.

But the old city name has remained synonymous with the battle and Volgograd lawmakers have decided to revive it for the anniversary and five other days of the year.

Putin has never denied Stalin's murderous purges of innocent citizens and deadly forced collectivisation.

But he and other modern leaders have preferred to overlook the disastrous errors in military strategy Stalin made during the war.

And Putin in particular has preached a patriotic message since returning to the presidency in May after serving four years as premier.

Analysts believe this has helped him maintain support among many of the older middle class voters in the face of the first street protests of his rule among the young.

Putin told the veterans that "no country can live without (patriotism) because otherwise it will simply dissolve like a lump of sugar in a cup of tea."

State media had focused their attention on Volgograd throughout the week as they detailed the lavish preparations and Kremlin's attention to veterans.

The commemorations were broadcast live on the national news channels while state television broadcast a new dramatised documentary about the "battle that changed world history".

Afternoon broadcasts also relayed a special message from the Russian crew members of the International Space Station -- a tradition usually reserved only for the highest national holidays.

"We extend our wholehearted congratulations," said ISS member Roman Romanenko.

"We will always be grateful for your feat. Its memory will live on for centuries."

But not everyone was pleased that this memory now appeared to be once again firmly associated with Stalin's name.

"This was a mistake," said a woman who agreed to only give her first name Larisa.

"We are overestimating Stalin's role in the war," she said. "He was bloodthirsty."