Moscow: A Russian opposition leader and fierce critic of President Vladimir Putin, Boris Nemtsov, was shot dead by an unidentified attacker who fired multiple rounds at the politician as he was walking in central Moscow late Friday.
The murder of the 55-year-old politician, who has been an outspoken critic of Russia's involvement in Ukraine, came ahead of a major opposition rally this weekend.
US President Barack Obama condemned the "vicious murder" of Nemtsov, whom he had met on a visit to Moscow, and called on the Russian government to conduct a prompt and impartial investigation of the killing, which sent shock waves across Russia.
The Kremlin swiftly dubbed his death a provocation.
The murder "bears the hallmarks of a contract killing," Putin spokesman Dmitry Peskov said, adding it was a provocation.
Police and investigators said Nemtsov was shot down by unidentified assailants as he was walking with a woman along a bridge not far from the Kremlin.
"A man with documents in the name of Boris Yefimovich Nemtsov was killed," an interior ministry spokesman told AFP early Saturday.
The Investigative Committee, which reports directly to Putin, confirmed Nemtsov's death, saying it had opened a criminal probe.
"According to preliminary information, an unidentified person shot at Boris Nemtsov no fewer than 7-8 times from a car as he was walking along the Bolshoi Moskvoretsky bridge," investigators said in a statement.