Police are offering a 1 million ruble ($31,000) reward for any information leading to the capture of a man suspected of killing more than 30 elderly women in the Volga Federal District.
The authorities also asked all single elderly women in the Sakhalin region to be vigilant.
The killer, who targeted elderly women living alone, introduced himself as a member of a homeowners' association or a social service employee to enter his victims' apartments in Kazan and other cities in the Volga Federal District, the Investigative Committee said in a statement. He then strangled the women and burglarized their homes.
The killer may since have fled the Volga region, possibly moving to the Far East, the statement by the committee's Sakhalin region branch said.
Witnesses described the killer as an athletically built man aged 20 to 35, 170 to 175 centimeters (5'7" to 5'9") high, who was seen wearing a dark hooded jacket, black pants and running shoes.