Outspoken Russian opposition leader Boris Nemtsov shot dead

Boris Nemtsov, the former Russian deputy prime minister and fierce critic of Vladimir Putin, has died after being shot four times by a passing car in Moscow, officials have confirmed. The 55-year-old was targeted by an unidentified attacker near the Kremlin during the early hours of Saturday morning - and was shot in the back. According to colleagues, he was working on a report which apparently included concrete evidence that Russia was directly involved in the separatist movement which erupted in Ukraine last year. At the time of the attack, Mr Nemtsov (pictured) was walking along a bridge with a Ukrainian woman, who was uninjured in the shooting. She is now being questioned by police.

[The murder] bears the hallmarks of a contract killing.

Putin spokesman Dmitry Peskov

A senior opposition politician, Mr Nemtsov was an outspoken detractor of Vladimir Putin’s administration - and had planned to attend an “anti-crisis march” through the capital on Sunday. Meanwhile, the White House has demanded that the investigation is “prompt, impartial and transparent”. President Obama, who met Mr Nemtsov in 2009, described him as a “tireless advocate” for the rights of Russian citizens, and cited his work in fighting corruption. In a statement, Britain’s Foreign and Commonwealth Office said it was “shocked and saddened” by the news. “We deplore this criminal act. Those responsible must be brought to justice,” it added.

I admired Nemtsov’s courageous dedication to the struggle against corruption in Russia and appreciated his willingness to share his candid views with me when we met in Moscow in 2009.

U.S. President Barack Obama