A security services source told the Russian news agency Ilya Pyanzin was extradited Saturday to Russia from Ukraine.
"The suspect, Pyanzin, has been remanded in pretrial detention facility No. 2 at Lefortovo and investigators from the Federal Security Services are likely to start working with him today," the source was quoted as saying.
Pyanzin and another suspect, Adam Osmayev, were arrested in January in Odessa. Ukrainian intelligence services said Pyanzin and Osmayev confessed their involvement in an assassination plot allegedly ordered by Chechen militant Doku Umarov.
Osmayev's extradition was suspended last week after the European Court of Human Rights said it would review the case. Osmayev has denied plotting to kill Putin, RIA Novosti said.