President Vladimir Putin has promised that everything will be done to find Boris Nemtsov's murderers.

"Everything will be done to give the organizers and executors of this base and cynical murder the punishment they deserve," the Russian president's office quoted Putin as saying in a message of condolences to Nemtsov's mother, Dina Eidman.

"Boris Nemtsov has left a trace in the history, politics, and public life of Russia. It fell to his share to hold significant official posts in what was a difficult transitional period for our country. He always stated his position in a straightforward and honest way, and defended his point of view," Putin said in his message.