Nemtsov was killed while walking across a bridge near St. Basil’s Cathedral with a woman from Ukraine around 11:15 p.m. local time Friday, according to Interior Ministry spokeswoman Elena Alekseeva. A car approached and several shots were fired, four of which hit Nemtsov in the back, she said.
At least seven or eight shots were fired, the Russian Investigative Committee said on its website.
Nemtsov’s murder caused the abrupt cancellation of a rally he and other opposition leaders had been planning for March 1 in Moscow that they had hoped would attract as many as 100,000 people. The organizers will instead seek to hold a march mourning Nemtsov on the same day, opposition leader Mikhail Kasyanov said.
“This is not a provocation, this is a reprisal,” said Kasyanov, a former prime minister. “It’s intimidation; we won’t be frightened. It’s up to the investigators to determine who ordered the shooting.
‘‘I am sure that the opposition will pull together more tightly,” he said.
Nemtsov had been getting death threats and was working on a report about Putin and Russia’s involvement in the civil war in Ukraine, according to Ilya Yashin, an opposition leader.
In 2011, he wrote a report in 2011 entitled “Putin. Corruption,” that focused on how the the leader’s friends and relatives benefited and on the perks Putin enjoys as head of an oil-rich state. Putin was prime minister at the time.
In that report, Nemtsov wrote that corruption had “reinforced Putin’s main management principle: For friends — anything, for the rest — mayhem. Obedience to the law and justice aren’t a requirement for civil servants in the Putin regime. Most important is personal loyalty.”
Putin’s spokesman, Dmitry Peskov, said by phone that “the president noted that there are all the signs that this was a hit and also an extreme provocation.”
Separately, Peskov told the Interfax news agency that Putin had ordered an investigation into “this cruel murder.” The president “expresses deep condolences to relatives and friends of Boris Nemtsov, who died tragically, Peskov said.
Nemtsov’s killing comes as the U.S. and its European allies are locked in the most-tense standoff with Russia since the Cold War. The U.S. and European Union imposed economic sanctions on Russia after Putin moved to annex the Crimea from Ukraine last year, and accuse him of fomenting an armed separatist revolt in eastern Ukraine, a charge Putin denies.
The Obama administration in Washington condemned Nemtsov’s ‘‘brutal murder” and in a statement released via Twitter called on the Russian government to conduct an impartial and transparent investigation.
“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 said in an e-mailed statement from the White House.
Secretary of State John Kerry said Nemtsov had “committed his life to a more democratic, prosperous, open Russia.” In every role Nemtsov played, Kerry said in a statement, he “sought to reform and open Russia, and to empower the Russian people to have a greater say in the life of their country.”
Nemtsov was “the smartest, strongest and most resolute of all the opposition leaders,” although his standing with the Russian public had been damaged by a campaign of “vilification” by state-controlled media, said Russia scholar Peter Rutland of Wesleyan University in Middletown, Connecticut.
He described Nemtsov as “a smart and charismatic figure who could have been a great Russian leader, in a different Russia.”
Other Putin critics who have been killed in recent years include Alexander Litvinenko, a former Russian spy who died in London in 2006 after drinking radioactive tea, and Anna Politkovskaya, a journalist who chronicled corruption under Putin and human-rights abuses during Russia’s conflict with separatists in Chechnya, who was gunned down in 2006.
Nemtsov, 55, rose to prominence in the 1990s as a pro- reform politician during the presidency of Boris Yeltsin shortly after the collapse of the Soviet Union.
He was governor of Nizhny Novogorod, a region that was associated with early efforts to promote a market-oriented transformation of the Russian economy. He then went to Moscow to become a deputy prime minister under Yeltsin.
After Putin succeeded Yeltsin in late 1999, Nemtsov became a critic and a leader of the opposition movement.
He also served as an adviser to former Ukrainian President Viktor Yushchenko, who was swept into power by that country’s 2004 Orange Revolution. Putin has frequently warned that those events could serve as a model for Russian anti-government activists.
“It’s quite symbolic that it’s liberal politicians who get assassinated in Russia and the market probably won’t like it,” Ian Hague, a founding partner at New York-based Firebird Management LLC, which oversees about $1.1 billion in assets including Russian stocks, said by phone.
“A lot depends on the facts around the case,” Hague said. “If it emerges that it was politically motivated, the market reaction could be bad.”
Rutland, the Russia scholar, said markets may take the killing in stride because they have already “priced in the fact that Putin is solidly in power.”
At the same time, he said, “the fact that individuals can be shot down in the middle of Moscow with such ease is a worrying reminder of how lawless Russia has become, a return to the violent years of the mid-1990s. So that fact alone should deter investors — who anyway were holding back because of the sanctions and ongoing confrontation in Ukraine.”