MOSCOW — Thousands of people gathered in central Moscow to remember Boris Nemtsov, the Russian opposition leader gunned down in the shadow of the Kremlin just before midnight on Friday, as police continue the hunt for his killer.

Nemtsov, a former deputy prime minister turned staunch government critic, himself had planned and promoted the march on Sunday to protest against the economic policies of President Vladimir Putin and the ongoing war in eastern Ukraine, in which the Kremlin denies playing any role despite a preponderance of evidence proving otherwise.

"I'm not afraid", "No words", "Propaganda murders" at Nemtsov mourning demo in Moscow http://t.co/ydzOFCHmVG pic.twitter.com/YLBv1tGiIR — Feldman (@EvgenyFeldman) March 1, 2015

Disconcerting to have a large opposition march in Moscow and not have Nemtsov standing at the front of the crowd. Unthinkable for a decade. — Glenn Kates (@gkates) March 1, 2015

Instead, the demonstrators whom he urged to turn out on Sunday mourned his death. They met at Slavyanskaya Square, near the Kitay-Gorod metro station, before marching to the bridge over the Moskva River where the charismatic 55-year-old Nemtsov was shot in the back and killed.

Moscow city authorities approved the march from 3 p.m. (7 p.m. EST) for up to 50,000 people, according to organizers, who said at least that many showed up.

Nemtsov mourning demo started 20min ago and this is the crowd awaiting to be searched by police on the starting point pic.twitter.com/vQTzwDC1qt — Feldman (@EvgenyFeldman) March 1, 2015

Russian opposition activists hope the mourning march will serve to catalyze their beleaguered and marginalized opposition movement — for which Nemtsov now serves as a martyr and a symbol — and not simply a one-off rally.

Watch the march live

Rallies for Nemtsov held across Russia

As people started to gather in central Moscow around 1 p.m. local time, one woman told a Radio Svoboda reporter she had come to protest against Putin's "vlast," a word that can mean both authorities and power.

Valeriy Borschev, a politician, came to the march with a small bouquet to leave for his old friend Nemtsov at the spot where he was shot.

"I knew Boris for many years," Borschev told Mashable. "His was a policy that placed human rights at the forefront. And he always spoke for the unification of the opposition. For example, he supported me in the elections. This is a politician who was so needed in Russia, and [his death] is a great loss for the country."

Thousands of people march through Moscow to mourn the death of Boris Nemtsov on Sunday, March 1, 2015.

Natalia, a lecturer for Moscow State University's geology department, came wrapped in a blue and yellow Ukrainian flag, "because there is a war in Ukraine and Russia has organized this war... and I am a Russian woman, but with Ukrainian roots."

Natalia, who did not give her last name, said she had listened to Nemtsov's last interview on Ekho Moskvy radio hours before he was killed, and only learned of his death when she left her home to walk her dog. "For me it is a tragedy," she told Mashable.

Many other people held signs reading "I'm not afraid," "No words" and "Propaganda kills."

'I'm not afraid', 'Propaganda kills' on posters at the march for Boris Nemtsov pic.twitter.com/nAZS7CEi1S — Paul Gypteau (@paulgypteau) March 1, 2015

Powerful. MT @KevinRothrock: "Four bullets" (followed by names of Russia state TV networks). Nemstov was shot 4 times pic.twitter.com/9v5cdlUKlX — Christopher Miller (@ChristopherJM) March 1, 2015

While it is hard to say for sure how many people came out Sunday, organizers put the number over of the expected 50,000 — some said it was closer to 100,000 — while authorities suggested the number of demonstrators was much smaller.

Numbers game. Police say ~7,000 people at #Nemtsov rally, but that seems like low estimate. Organizers say ~50,000, which may be high. — Christopher Miller (@ChristopherJM) March 1, 2015

Nemtsov mourning demo's first lines pic.twitter.com/0keoNdSf4M — Feldman (@EvgenyFeldman) March 1, 2015

People forever. Must be largest opposition rally in #Moscow since Bolotnaya. Prob bigger than some of those rallies. pic.twitter.com/lBOVEQI8rN — Christopher Miller (@ChristopherJM) March 1, 2015

Many people carried the white, blue and red Russian flag, and bouquets of flowers. As one journalist pointed out, florists near Slavyanska Square were busier than usual Sunday afternoon.

Long queues at florists at metro near nemtsov mourning march pic.twitter.com/hNCRxg1ahd — tom balmforth (@BalmforthTom) March 1, 2015

Others carried placards calling Nemtsov a hero.

And there was a massive police presence to ensure security at the demonstration.

Police lined up on march route next to bridge where nemtsov killed pic.twitter.com/aanZgpMXXk — tom balmforth (@BalmforthTom) March 1, 2015

Thousands of others participated in rallies across Russia, from St. Petersburg to Yekaterinburg.

В Петербурге 10 тысяч. Не меньше. pic.twitter.com/iNuolM1jXb — Арсений Веснин (@ars_ves) March 1, 2015

Hundreds come out to remember Nemtsov at Yekaterinburg march @RFERL pic.twitter.com/DSMcg5EwVU — Alec Luhn (@ASLuhn) March 1, 2015

In the southwestern Russian city of Voronezh, activists from the pro-Kremlin Anti-Maidan movement reportedly disrupted a small anti-Kremlin demonstration.

Dressed as Cossacks, the provocateurs splashed Zelyonka, a green antiseptic, on rally-goers.

People of all ages and classes came out to protest against the government and memorialize Nemtsov, whose energy and charisma was magnetic. Older women in particular were big fans of the opposition politician, especially in his "young reformer" days in the 1990s.

Nemtsov was best of 90s Russia: fresh, normal, Clintonian flair for retail politics (and other BC vices), fun and hopeful. The antiPutin. — Matthew Kaminski (@KaminskiMK) March 1, 2015

"Nemtsov is love, Putin is war" pic.twitter.com/Dh2YzOBdxu — tom balmforth (@BalmforthTom) March 1, 2015

As the crowd began to march, they chanted "Russia without Putin!" and "Russia will be free!"

The crowd began to move. Somewhere in the beginning people are chanting "Russia without Putin". pic.twitter.com/fWSrL9wKpn — Alexander Roslyakov (@RoslyakovAP) March 1, 2015

While demonstrators flooded central Moscow, there was no mention of the massive march in the parallel universe that is state-sponsored Russian media. However, Only Russia's state-run international English-language outlets RT and Sputnik are covering it.

57 Channels and theres nothing on: Russian state TV blackout so far on the #Nemtsov march. Have to turn to foreign media Sky, CNN, Euronews — Jason Corcoran (@jason_corcoran) March 1, 2015