An entire section of the 12-storey residential building collapsed when a gas explosion tore through the high-rise in the industrial city of Magnitogorsk nearly 1,700 kilometres (1,050 miles) east of Moscow in the Ural mountains.
"Three people have been pulled alive from the rubble and three are dead," Boris Dubrovsky, governor of the Chelyabinsk region where the city is located, said in a statement.
Officials said that the fate of 79 people was unclear, with police working to locate their whereabouts.
The Soviet-era high-rise was built in 1973 and was home to around 1,100 people. The residents have been evacuated.