34 were killed and 150 wounded in the blast
The blast ripped through the main street of the town of Kaspiysk in the southern Russian republic of Dagestan as soldiers and civilians marched to commemorate the 57th anniversary of Russian victory in World War II.
Police in Dagestan, the region bordering the breakaway republic of Chechnya, said that 150 people had been injured in the explosion.
'Mound of bodies'
The victims included children, military veterans and musicians, as well as at least 19 soldiers said to be among the dead.
"The scene is horrifying. There are body parts everywhere and an overpowering smell of blood," a correspondent for Russia's NTV station said.
The town's medical services were overwhelmed and many of the injured were taken to the regional capital Makhachkala, 20 kilometres (12 miles) north of Kaspiysk.
'Scum'
"I think that few people can have any doubt about this being an act of terrorism," said Russian President Vladimir Putin, who was addressing a rally in Moscow's Red Square at the time of the blast.
He said the act on "the most dear of all holidays... was committed by scum who hold nothing sacred," comparing those behind the suspected attack to Nazis.
Russian police told the Reuters news agency that nuts, bolts and nails were packed into the mine to cause maximum injury.
New tactic?
Mr Putin instructed the director of Russia's Federal Security Service (FSB), Nikolai Patrushev, to fly to Dagestan immediately to coordinate an investigation into the incident.
The BBC's Nikolai Gorshkov in Moscow says Russians are shocked at the incident on one of the country's most solemn and sacred occasions.
Our correspondent says mines on roadsides have been widely used to target Russian troops in Chechnya, and their use against a parade which included civilians outside the war-torn province would be a departure from previous tactics.
So far no one has claimed responsibility for the explosion.
Grozny attack
In a separate incident, civilians and Russian forces came under attack at a Victory Day parade in a stadium in the Chechen capital, Grozny.
Police officials said shots had been fired from grenade launchers.
One police officer is reported to have been wounded.
Earlier reports said that a mine disposal unit had detonated a landmine found at the stadium before the Victory Day events got under way.
Drawn-out war
Dagestan sees frequent small-scale bombings and other unrest, often related to the 31-month war between separatist rebels and Russian forces in the neighbouring breakaway region of Chechnya.
Kaspiysk suffered a large bomb attack in November 1996.
Sixty-eight people were killed when an explosion tore through an apartment building housing Russian border guards.
The cause of the blast was never determined, but many blamed it on Chechen rebels.