AFP, Moscow :Western leaders on Saturday condemned the drive-by shooting of Russian opposition leader Boris Nemtsov, a fierce critic of President Vladimir Putin, as he was walking across a bridge near the Kremlin.US President Barack Obama decried the “brutal” and “vicious murder” of Nemtsov, which came ahead of a major opposition rally planned for Sunday, and called on Russia to conduct an impartial probe.French President Francois Hollande called the killing a “hateful murder” of a “defender of democracy”.A constant stream of people laid flowers and set candles at the site of the murder on Saturday morning, with police closing off one lane of traffic to let them through, an AFP reporter saw.The Kremlin said Putin had taken personal control of the investigation.Putin’s spokesman Dmitry Peskov said the murder of the 55-year-old former deputy prime minister bore “the hallmarks of a contract killing” and described it as a provocation.The last Soviet leader Mikhail Gorbachev, quoted by Interfax, said the killing was aimed at “destabilising the situation in the country, at heightening confrontation” with the West.The brazen assassination was one of the highest-profile killings during Putin’s 15 years in power and recalled the shooting of anti-Kremlin reporter Anna Politkovskaya, who was gunned down on Putin’s birthday in 2006. Investigators said Nemtsov was shot by unidentified assailants from a white car as he was walking with a woman along a bridge just metres (yards) from the Kremlin.The woman was identified as Ukrainian model Anna Duritskaya by Life News website.”According to preliminary information, an unidentified person shot at Boris Nemtsov no fewer than seven or eight times from a car as he was walking along the Bolshoi Moskvoretsky bridge,” said investigators.Interior ministry spokeswoman Yelena Alekseyeva said four bullets struck Nemtsov.An AFP reporter saw blood on the rain-soaked pavement on the side of the bridge near the red walls of the Kremlin, and roses lying beside a police barrier at the scene. Speaking on radio just hours before his murder, Nemtsov sounded upbeat and urged Russians to join a major opposition rally planned for Sunday. “The key political demand is an immediate end to the Ukraine war,” he said on popular Echo of Moscow radio, adding that Putin should quit.The current regime has reached “a dead-end in both domestic and foreign policies. They should go,” said Nemtsov, who reportedly was compiling a report on Russia’s involvement in the Ukraine conflict.After working as a research scientist in the late Soviet era, Nemtsov rose to prominence as governor of the Nizhny Novgorod region in central Russia and became a vice prime minister in the late 1990s under the presidency of Boris Yeltsin.After leaving parliament in 2003, he led several opposition parties and groups.A passionate orator with a rock star image and popular with women, Nemtsov was a key speaker at mass opposition rallies against Putin’s return to the Kremlin in 2012.He wrote a series of reports critical of corruption and misspending under Putin.In 2013, he said up to $30 billion of the estimated $50 billion assigned to the Olympic Games that Russia was to host in Sochi had gone missing.”This is payback for the fact that Boris consistently, for many, many years fought for Russia to be a free democratic country,” opposition leader Mikhail Kasyanov, who served as prime minister under Putin, told reporters after visiting the murder scene.”In the 21st century, in 2015, a leader of the opposition is shot dead by the Kremlin walls. It is beyond imagination.”Washington led condemnation of the killing.”We call upon the Russian government to conduct a prompt, impartial and transparent investigation into the circumstances of his murder and ensure that those responsible for this vicious killing are brought to justice,” Obama said in a statement.Hawkish US Senator John McCain said he was “devastated” by Nemtsov’s murder and that “Boris is dead because of the environment of impunity that Vladimir Putin has created in Russia.”