Tens of thousands of people marched in central Moscow Sunday to mourn murdered opposition leader Boris Nemtsov.
Many of the somber marchers carried Russian flags and placards saying, "I am not afraid," in memory of the veteran liberal politician and vocal critic of President Vladimir Putin. Organizers said 70,000 people joined the march, while Moscow police said the crowd was much smaller, about 21,000.
Some of the marchers, young and old, carried pictures of the 55-year-old Nemtsov, who was shot dead Friday night on a bridge near the Kremlin while he was walking home from a restaurant.
Former Russian prime minister Mikhail Kasyanov, a staunch critic of Putin, said he thinks the killing will prove to be a significant event in Russia's history.
"I understand, and I believe," Kasyanov said, "that this tragic event which happened two days ago is absolutely a turning point for the whole history of new Russia, a turning point because of simple reason: that people who before thought that they could quietly sit in their kitchens and simply just discuss problems within the family, now they will start reconsidering everything that's going on in our country."
'Russia without Putin'
VOA's Daniel Schearf, reporting from Moscow, said some protesters, as they neared the bridge where Nemtsov was killed, briefly chanted, "Russia without Putin!"
The crowd was largely somber, but they did chant slogans, including "never forget, never forgive," Radio Free Europe/Radio Liberty reported Sunday.
Russian authorities, usually slow to give permission for large opposition rallies, gave quick approval for the memorial march.
Nemtsov was to have led an anti-war and anti-Putin rally in Moscow Sunday. Instead, the memorial was planned for the man whom U.S. President Barack Obama called a "tireless advocate" for the rights of the Russian people.
Police are hunting for those responsible for shooting Nemtsov four times from a car while he and a female companion crossed a bridge over the Moscow River Friday night, just steps from the Kremlin. The woman was not hurt.
Mourners have continued to leave hundreds of flowers at the site where Nemtsov was killed.
Meanwhile, Ukrainian Deputy Oleksiy Goncharenko was detained at the demonstration and may be charged in connection with a fire last May at the Odessa trade union building that killed over 40, according to Interfax.
Putin to oversee investigation
Russian President Vladimir Putin said the shooting looks like a contract killing, and he called it a "provocation." The Kremlin said he will personally oversee the investigation.
Authorities announced Sunday a reward of 3 million rubles -- about $50,000 -- for information about Nemtsov's murder.
U.S. Secretary of State John Kerry said the United States does not have any intelligence on who murdered Nemtsov. He called on Russian authorities to conduct a thorough investigation "not just of who actually fired the shots, but who, if anyone, may have ordered, instructed this or been behind this."
Putin sent a condolence letter to Nemtsov's mother, Dina Eidman, saying he sincerely shares her sorrow, and calling Nemtsov's death an irreparable loss.
But just a few weeks ago, Nemtsov told the Russian news website Sobesednik he thought Putin wanted him dead, and he did not hold back his contempt for the Russian leader.
"I'm afraid Putin will kill me. I believe that he was the one who unleashed the war in Ukraine. I couldn't dislike him more," Nemtsov said.
Ukrainian President Petro Poroshenko condemned Nemtsov's murder, calling him a "bridge" between Ukraine and Russia.
President Obama called the killing "brutal" murder, and said Russia must carry out a prompt and impartial investigation.
France's President Francois Hollande expressed anger at Nemtsov's death. He called the shooting a "hateful murder," and described Nemtsov as a "defender of democracy."
Attempt at destabilization
Russia's Investigative Committee commented that it is possible the crime could be an attempt to destabilize the political situation. Spokesman Vladimir Markin said Saturday it also could be linked to Islamic extremism or the situation in Ukraine.
Putin's opponents said such suggestions show the cynicism of Russia's leaders as they whip up nationalism, hatred and anti-Western hysteria to rally support for his policies on Ukraine and deflect blame for an economic crisis.
“It is a blow to Russia. If political views are punished this way, then this country simply has no future," Sergei Mitrokhin, an opposition leader, told Reuters of Nemtsov's murder.
Some media outlets blamed the murder on nationalists, who have been accused of several assassinations, including that of human rights lawyer Stanislav Markelov in 2009.
“I flatly deny any involvement of nationalists in these events,” Dmitry Dyomushkin, a leader of “The Russians” nationalist organization, told Reuters.
Some in Moscow appeared to agree with officials that the opposition, struggling to make an impact after a clampdown on dissent in Putin's third spell as president, might have killed one of their own.
“The authorities definitely do not benefit from this. Everybody had long forgotten about this man, Nemtsov. ... It is definitely a 'provocation,' ” said one Moscow resident, who gave his name only as Denis.
Nemtsov was a deputy prime minister in the 1990s, and many Russian observers predicted he would succeed then-President Boris Yeltsin.
After Yeltsin chose Putin as his successor, and Putin's subsequent election in 2000, Nemtsov became one of Russia's sharpest and most outspoken Putin critics, especially since last year's uprising in Ukraine.
In September, Nemtsov told VOA that Putin wants revenge for Ukraine's overthrow of its pro-Russian president.
He said Putin fears that what happened in Ukraine could happen in Russia, and sees a pro-European Ukraine as a threat to his own power.
Nemtsov's funeral is likely to be held at Moscow's Troyekurovsk Cemetery on Tuesday, RFE/RL reported.
Vladimir Markin of the Russian Investigative Committee said, "Currently the investigation is looking into several lines of inquiry. First of all of course, it is the possibility that the murder could be a provocation to destabilize the political situation in Russia. And Nemtsov could become a sacrificial victim for those who would not stop before using any means to reach their political goals."
"Also we are closely looking into a possibility that the murder could have links with Islamist extremism. The investigation has information that Nemtsov received threats linked to his position about the shooting at the Charlie Hebdo magazine office in Paris," Markin added.
"Besides, we are already checking a line of inquiry linked to the events inside Ukraine. It is no secret that on both conflicting sides there are very radical individuals not controlled by any authorities," he said.
Daniel Schearf provided some material for this article. Some material for this report came from Radio Free Europe/Radio Liberty and Reuters.
People carry a huge banner reading "Those bullets for everyone of us, heroes never die!" as they march in memory of opposition leader Boris Nemtsov who was gunned down on Friday near the Kremlin, in Moscow, Russia, March 1, 2015.
People carry portraits of opposition leader Boris Nemtsov, who was gunned down on Friday near the Kremlin, with words reading "He fought for a free of Russia, He fought for our future!" in Moscow, Russia, March 1, 2015.
The Russian national flag is pictured during a march to commemorate Kremlin critic Boris Nemtsov, who was shot dead on Friday, in Moscow, March 1, 2015.
Riot police stand guard during a march by opposition supporters to commemorate Kremlin critic Boris Nemtsov, who was shot dead on Friday night, in Moscow, March 1, 2015.
Flowers and pesters reading "Propaganda kills! Fight!" are seen at the place where Boris Nemtsov was gunned down on Friday near the Kremlin, with St. Basil Cathedral is in the background, in Moscow, Russia, March 1, 2015.
People carry Russian national flags as they march with posters reading "I have no fear, fight!" near the place opposition leader Boris Nemtsov was gunned down on Friday, near the Kremlin, in Moscow, Russia, March 1, 2015.
Opposition leader and Russia's former Prime Minister Mikhail Kasyanov, right, speaks to the media with opposition activist Ilya Yashin, left, during a march to commemorate Kremlin critic Boris Nemtsov, who was shot dead Friday, in Moscow, March 1, 2015.
Dmitry Gudkov, a member of the Russian parliament, attends a march to commemorate Kremlin critic Boris Nemtsov, who was shot dead Friday, in Moscow, March 1, 2015.