The footage appeared only hours after tens of thousands of people rallied in Moscow and other cities to protest the deaths of more than 335 people in Beslan, near Chechnya, in the worst hostage-taking in Russian history.
The 87-second tape showed pools of blood coming from the crowds of people and a streak of blood running across the centre of the gym which was being wired.
Wires also ran between the two basketball hoops on opposite sides of the gym. They were stuffed with bombs on both sides and several other explosives were hanging from the wires.
"Do not bring in the children here yet," one man was heard yelling in accented Russian as another continued to connect the wires.
The tape also showed a female human bomber completely draped in black concealing herself in a dark side room. She held a pistol and wore suicide belts.
Huge protests were held across
Russia against the siege
The footage was broadcast on a day when hundreds of thousands of people gathered for "anti-terror" rallies throughout Russia amid mounting rage over the bloody end to the hostage siege in North Ossetia.
On Tuesday, scores of schoolchildren killed in the siege were laid to rest in an overflowing cemetery amid wrenching grief in the town of Beslan, in the southern republic of North Ossetia.
A three-day stand-off at Beslan's main school ended in carnage on Friday after security forces stormed the building following a series of explosions.
Officials say 18 of the estimated 1000 people held hostage by separatists demanding independence for Chechnya are still unaccounted for, their families unable to find them either in morgues or hospitals.
The catastrophe was the worst of its kind in modern Russian history and was only the latest in a string of recent attacks that included the downing of two passenger jets and a bombing outside a crowded Moscow subway station.
Unlike those attacks, however, the bloodshed in Beslan has sparked a primal anger in some Russians that the government is struggling to dispel.
Beslan residents continue the
grim task of burying their dead
The Russian press lashed out at President Vladimir Putin, saying his efforts to link separatist fighters in Chechnya with international terrorism was a cynical ploy to escape blame for his uncompromising policy on the fighters.
But mounting criticism against Putin and the government has been countered by displays of nationalist fervour and a surge of rage against "terrorists" who carried out the attacks in Russia.