Russian investigators have identified the "mastermind" behind the murder of Putin critic Boris Nemtsov, state media has reported.

Russia's Investigative Committee has identified the person who gave weapons, a vehicle and money to the man who allegedly murdered the Russian opposition politician, a source close to the investigation told Kommersant.

According to the newspaper, the man, named only as Ruslik, promised those allegedly responsible 5 million rubles ($825,000) for carrying out the hit.

Zaur Dadaev, one of five Chechen's arrested for the attack, confessed to killing Nemtsov, then withdrew his confession, claiming he had been tortured.

Experts believe that the Nemtsov killing has exacerbated longstanding tensions between the FSB and Chechen security services. The FSB is said to have pursued the Chechen suspects as a means of pegging back the growing ambition of Chechen leader Ramzan Kadyrov, who praised Dadaev as a "true Russian patriot" in the wake of the killing.

Independent newspaper Novaya Gazeta has published a list of opposition figures that are on a hit list allegedly compiled by a Chechen security official.