Thousands of mourners and dignitaries have filed past the white-lined coffin of murdered Kremlin critic Boris Nemtsov, many offering flowers as they paid their last respects to one of the most prominent figures of Russia's beleaguered opposition.
Mr Nemtsov was shot dead late on Friday while walking on a Moscow bridge near the Kremlin with a companion. No suspects have been arrested.
The killing has deeply shaken Russia's small and marginalised opposition movement. Many opposition supporters suspect the killing was ordered by the Kremlin in retaliation for Mr Nemtsov's ardent criticism of President Vladimir Putin, while authorities have suggested several possible motives, including a provocation aimed at tarnishing Mr Putin's image.
The line of mourners stretched for hundreds of metres and included people both young and old.
"He was our ray of light. With his help, I think Russia would have risen up and become a strong country. It is the dream of all progressive people in Russia," said 80-year-old Valentina Gorbatova.
Mr Nemtsov, 55, had been a deputy prime minister under former president Boris Yeltsin and was widely seen as a rising young reformer. However, in the Putin era Mr Nemtsov's party lost its seats in parliament.
Although his influence in mainstream politics vanished, Mr Nemtsov remained visible as one of Mr Putin's most vehement critics. Just a few hours before his death, he conducted a radio interview in which he denounced Mr Putin for "mad, aggressive" policies in the Ukraine crisis.
His body lay in a coffin in the Sakharov Centre in central Moscow, named after the late Soviet-era dissident and Nobel Peace Prize laureate Andrei Sakharov. The funeral and burial are to be held in the afternoon.
Among those attending the viewing were US ambassador John Tefft and former prime minister Mikhail Kasyanov, who has gone over to the opposition. Russian deputy prime ministers Sergei Prikhodko and Arkady Dvorkovich and Mr Yeltsin's widow Naina also came, according to Russian news reports.
"They probably know that if they don't come, then at some point people will be coming for them," Irina Khakamada, co-leader of a liberal party in parliament with Mr Nemtsov, said of the Russian government officials.
Veteran human rights activist Lev Ponomarev echoed the view of many opposition figures that the strong nationalism and intolerance of dissent that has risen up under Mr Putin and is on display on Russian state-controlled television has coarsened society and encouraged violence.
"In this atmosphere of violence and hate, these killings will only continue," he said.
Many commentators said that, like other key opposition leaders, Mr Nemtsov was constantly being shadowed by police, so it would be hard to imagine that his killing could go unnoticed by them.
Some noted that Mr Nemtsov died on the newly established holiday commemorating the special operations forces, honouring troops who swept through Ukraine's Crimean Peninsula, setting the stage for its annexation by Russia a year ago.
Mr Nemtsov's killing was the biggest political assassination in Russia since 2006, when another Kremlin foe, journalist Anna Politkovskaya, was shot dead in the lift of her Moscow apartment building on Mr Putin's birthday. Five Chechens were convicted in the case last year, but it has remained unclear who ordered the killing.
Some observers speculated that certain members of a hawkish, isolationist wing of the government could have had a hand in Mr Nemtsov's death, possibly counting on it to provoke outrage abroad and further strain Russia's ties with the West.
Those relations are already at their lowest point since the Cold War because of the fighting in eastern Ukraine.
The government in Kiev blames Russia for supporting and arming the separatists. Russia denies the charge but Nato says it has satellite photos of Russian military equipment in eastern Ukraine.