The explosion which occurred at about 5 a.m. Moscow time (2 a.m. GMT) destroyed three apartments in a two-storey residential building. Rescuers said the blast was caused by a gas leak and did not cause a fire.
It took rescuers three hours to pull out the body of a 61-year-old woman and a search is continuing for a man believed to be in the building.
Meanwhile, eyewitnesses said another woman may have been in the building at the time of the blast. "According to relatives, people were in both apartments and they were possibly dead, it then turned out they hadn't spent the night at home," a spokesman said.
A crisis center has been established. An investigation is under way.
A wave of fatal gas explosions in residential buildings in Russia since the start of the year has left 21 dead and over 40 injured.
