The 30-year-old electrician, identified only as Dmitry K, lured victims to his house by posting adverts for computer equipment on the internet.
Police in Yekaterinburg, a city in Russia's Urals region, tracked the suspect down after finding the charred body of a law student in a roadside ditch.
Dmitry K admitted murdering the student, investigators said, before claiming that he had also killed several other victims as he conducted experiments on an improvised electric chair that he had invented.
The suspect, who worked at a local power plant, told detectives he would confess to the other murders if they found the bodies.
Police say they are investigating at least four other incidents in which Yekaterinburg residents went missing after responding to internet adverts for computer supplies over the past 12 months.
"There is reason to believe that the number of victims is higher," Vladimir Davydov, a senior detective in the Yekaterinburg police force, told reporters.
The dead student, named only as Anton A, was the first victim of the killer's research and was murdered in a correspondingly rudimentary way.
After persuading the student to come into his garage, Dmitry K overpowered his victim and then wrapped his body with copper wire connected to a generator. The suspect told police he hit a button on his computer which triggered a surge of current through the student's body, killing him almost instantly.
As he honed his technique, Dmitry K then fashioned an improvised electric chair which he used to practice on subsequent victims.
According to police, the suspect also claimed to have designed a doormat that would electrocute anyone who stood on it, but had yet to test it.
He also asked detectives to return a camera he had invented which used an electro-magnetic ray to erase the memory of anyone he photographed with it.
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