The man, a native of the Pskov region, has confessed to the killings, but police have not yet been able to confirm in his involvement in the crimes, RIA Novosti reported.
However, "there is enough of a basis to believe" he committed all the killings, said Igor Mezinov, a spokesman for the Interior Ministry's main criminal investigation unit.
Police believe the killings occurred in the Rostov and Pskov regions between September and December 2005.
The suspect entered the homes of single retirees who were at least 70 years old by offering to buy some of their household goods, the ministry said in a statement. Once in the home, he "assessed the situation" and determined whether to kill the person.
The ministry is also investigating whether he also had been involved in similar killings in Russia in 2004 and 2005.
The suspect is currently serving an eight-year prison sentence for robbery, officials said.