MOSCOW - Ahead of the third day of mourning for Russian opposition leader Alexei Navalny, who died suddenly in an Arctic prison, activists sent out safety tips for Russians wishing to lay flowers at memorials that have sprung up across the country, from St. Petersburg in the northwest to Magadan in the Far East; in the capital, Moscow, that was Navalny’s beloved home - and even in the Russian-occupied city of Luhansk in eastern Ukraine.

“Bring your passport. Keep a copy of the hotline for detainees. Bring water, a fully charged phone, and a powerbank,” one post stated. Navalny’s team, now operating in exile, also offered to pay any fines meted out to protesters.

Navalny, who was the most prominent challenger of President Vladimir Putin, often urged his supporters not to be afraid. And in the days after his death Friday at age 47 - his team says it was state-sponsored murder - hundreds have heeded Navalny’s call, risking arrest in the repressive climate of wartime Russia and braving bitter winter temperatures, to contribute to the piles of bouquets, which in some cases were quickly swept away by the authorities.

In other cases, it was the mourners who were swept away: at least 366 people have been arrested in 36 cities, including 200 in St. Petersburg, according to a watchdog group, OVD-Info, which tracks arrests. More than 29,000 people also put their names to a petition demanding that Navalny’s body be released to his family. On Saturday, his mother, Lyudmila Navalnaya, traveled to the town above the Arctic Circle where he died but could not reclaim his remains.

Just as the authorities delayed Navalnaya’s right to bury her son, they initially seemed intent on denying Navalny’s supporters any right to grieve. Videos flooded social media showing brutal arrests of people holding placards at the memorials. Teenagers were detained for laying flowers for a man who was envisioned by many as Russia’s Nelson Mandela - a persecuted dissident destined to emerge one day from prison and lead his country to a democratic future.

Some of those arrested now face two weeks in jail. In some towns, memorials were trashed by groups of security agents. On Saturday in Moscow, at a bridge on which Putin critic Boris Nemtsov was fatally shot in 2015 and that has since served as a symbolic memorial, men identifying themselves as “volunteers” ripped up flowers and smashed candles.

“I am a volunteer who fights against traitors to the fatherland,” said a man in a balaclava when challenged by one mourner. “Glory to Russia!”

But by Sunday, the mood in Moscow, at least, had shifted, with authorities seeming to accept that it was better to allow a steady flow of people to pay their respects. Really, what harm could it cause: Their hero - and their hopes - were dead.

At the Solovetsky Stone - a memorial honoring victims of the Soviet gulags, which stands across from Lubyanka, an infamous KGB prison that is now the headquarters of its successor, the FSB - a Washington Post reporter watched as 100 or so people approached the monument over the course of an hour, clutching red carnations and tulips.

Many wept. Some offered a prayer.

Mourners were politely directed by a dozen or so police officers who stood around the monument and instructed them not to spend more than a few minutes at the stone. Someone had placed a portrait of Navalny and his wife, Yulia Navalnaya, amid the stems. It was now submerged beneath snow and red roses.

A young couple, Yevgeny, 26, and Yulia, 24, who asked to be identified only by their first names for fear of repercussions, were in floods of tears. Together, they said, they had attended every protest led by Navalny since 2019.

“He was our chance at freedom - with him, we really had a hope that everything could change,” Yulia said.

“He was a politician who really loved Russia and loved its people. He tried to change what he could and actually talked to people,” said Yevgeny, wiping his eyes.

The couple said they were surprised by the conduct of the police officers on Sunday. They said they had prepared to get arrested and had brought their passports and the phone number of a lawyer.

Ilya Aminyan brought his 3-year-old son Iosef to lay flowers. “This is one of those moments in which we have to unite and be here together,” Aminyan said. “Such a person should not have died like that, especially at a time like this.” Aminyan said that he, too, had attended massive street protests led by Navalny - before he was poisoned, after he sought to run for president but was barred from the ballot because of trumped-up criminal convictions.

“He was a very important person - he became a symbol,” Aminyan said. “Honestly, he became a legend.”

The mourners interviewed on Sunday all said they recalled the “unforgettable” scenes on Moscow’s Sakharov Avenue when, first in 2011, then in 2019, Navalny led giant street rallies against Putin and government corruption.

Opposite Sakharov Avenue stands another memorial to political repression - known as the Wall of Tears - where on Sunday a trickle of people came to lay flowers. The site had been cordoned off and there was a heavy police presence. Riot officers and plain clothes security agents video-recorded mourners and checked documents. People were given just a few minutes to pay their respects before being ushered along.

Alexandra Popova, a political activist and the wife of the imprisoned poet Artyom Kamardin, remembered how Navalny joined protesters in 2019, when they stood outside the presidential administration building for months demanding the release of dozens of political prisoners. Navalny joined the picket line on several occasions with his wife, and brought tea.

“Navalny knew how to get a crowd even in bad weather,” Popova recalled on Sunday evening, as she walked through those same streets.

For Popova, the administration building and the nearby park in Moscow’s Kitai Gorod bring back painful memories. It was a time when young Muscovites still believed they could build or achieve something.

“All these streets, they are just filled with tears and pain and blood. So many people were beaten up, right here,” she said, walking past crowds of people on Bolshaya Nikitskaya on their way to dinner or drinks at one of the softly lit bars blaring pop music. “There’s a flow of people here too, but they don’t care – they don’t seem to care that Navalny has died.”

For Popova, whose husband, Kamardin, received a seven-year sentence in December for public readings of antiwar poetry, Navalny’s death in prison is especially sensitive.

She is perpetually worried about her husband’s physical and mental health.

“Navalny’s death shows us that absolutely no one is safe,” she said.

Putin, who made a point of virtually never uttering Navalny’s name aloud, still had not commented on his death as of Sunday. Putin’s spokesman, Dmitry Peskov, on Friday denounced accusations by world leaders that the Russian president was culpable, calling the allegations “unacceptable.”

Among close friends and associates of Navalny, the reality of his death seemed to still be setting in, but there was also no doubt in their minds who was responsible. Navalny teamed up with Bellingcat, the investigative news group, to prove that a team of FSB agents was responsible for attacking him with a banned nerve agent in 2020. And last week, his associates alleged, the Kremlin finally “finished it” - to use Putin’s phrase.

“Alexei Navalny wanted one very simple thing: for his beloved Russia to be just a NORMAL country,” Navalny’s longtime chief of staff and political adviser, Leonid Volkov, posted on X. “And for this Vladimir Putin killed him. Poisoned, imprisoned, tortured and killed him. Killed is not an exaggeration, not a figure of speech.”

“You can’t write about Alexei - he ‘died,’” Volkov continued. “This is not death, this is murder. Everything there is covered with cameras in the colony. Every step he took was filmed from all angles all these years. Each employee has a video recorder. For two days - there is not a single video: not leaked, not published. There is no room for uncertainty here.”

With most of the Russian political opposition, like Volkov, in exile, and long jail sentences now meted out for even a flicker of dissent, mass protests following Navalny’s death are virtually unthinkable. And analysts said that despite the emotional end to the bitter, long-running rivalry between Navalny and Putin, Navalny’s death is unlikely to be a turning point.

“Everyone is horrified, of course but this is a certain circle of people,” said Andrei Kolesnikov, a senior fellow at the Carnegie Russia Eurasia Center. “They are very few, and it’s clear they can’t make any protests.” Kolesnikov added: “There is the feeling we are in a police state.”

For some it was enough to be able to go out this weekend and stand in the snow alongside other mourners. “People are just constantly scared out of their wits,” Yulia, the 24-year-old woman outside Lubyanka, said. “This is a dictatorship where you cannot express yourself.”

Others have found creative, lower-risk ways to express their views. Some Russians lit candles for Navalny at local churches - confident that Putin’s regime, which has built a strong alliance with the Russian Orthodox Church - would not dare to interfere with Sunday worship.

Others posted comments commemorating Navalny on YouTube, in the comments section under “Alive,” the latest hit by the pro-war Russian pop singer Shaman, who had dedicated the song to “all who suffer for the truth.”

“Navalny will live forever!” one comment declared.

“Thank you for this song supporting Alexey … of course this song should become a hymn for all those who have suffered from injustice,” another post stated sarcastically.

Mikhail Khodorkovsky, the Putin critic and former Yukos oil tycoon who was jailed in Russia for a decade, has urged citizens to write in Navalny’s name on the ballot during next month’s presidential election.

“Putin must understand that even the elimination of leaders will not rid him of his opponents,” Khodorkovsky said in statements to The Post from his home base in London. “The Russian opposition has lost one of its brightest and most important leaders. This is a very heavy loss. We - the opposition, must respond to this crime with even greater coordination and interaction.”

Volkov, Navalny’s chief of staff, said his boss would insist that the opposition fight on:

“His life’s work must win.”

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Robyn Dixon, Mary Ilyushina and Natalia Abbakumova in Riga, Latvia, and Catherine Belton in London contributed to this report.