Amid freezing temperatures, firefighters put out the blaze just before dawn and pulled six bodies from under the debris, said Alexander Kulichenkov, a spokesman for the regional division of the Emergency Situations Ministry. The fire occurred on the site of a sporting complex that is under construction.
Three people were injured and one hospitalized, Kulichenkov said; the dead all appeared to be construction workers, reports AP.
The blaze appeared to have started when scaffolding caught fire, he said.
Russia records about 18,000 fire deaths a year roughly 10 times the rate in the United States. Experts say fire fatalities have soared since the collapse of the Soviet Union because of lax enforcement of safety standards.