More than 20,000 Russians marched through central Moscow Saturday to honor the memory of opposition politician Boris Nemtsov, who was killed in the shadow of the Kremlin one year ago.
Some marchers carried Russian flags, some placards, flowers and Nemtsov's portraits. Others chanted: "Russia will be free" and "Russia without Putin."
People also brought flowers and candles to the Bolshoi Moskvoretsky Bridge near the Kremlin walls where the 55-year-old Nemtsov was shot dead.
US ambassador lays wreath
U.S. ambassador to Russia John Tefft joined the mourners to pay tribute to Nemtsov and laid a wreath at the site with a ribbon saying "From the American people."
"I am here this morning with my deputy and my staff representing the president and the people of the United States to honor the memory of a man who we knew as a government official, as a politician and, for many Americans, as a friend," Tefft said. "We are here today to honor his memory, the values for which he stood and to express our hope for the future that some of the dreams that Boris Nemtsov had will come true in Russia."
WATCH: Russians Protest on Anniversary of Nemtsov Slaying
Russian authorities permitted the opposition to hold the march through the city center, but refused to allow a memorial march or a permanent marker at the bridge.
His allies have struggled to maintain a makeshift shrine there.
Mikhail Kasyanov, a former Russian prime minister and leader of the opposition Parnas Party, said that authorities did not allow the march to the bridge, fearing the symbolism of the murder place.
"I see that Muscovites supported our call [to join the march] and that Boris Nemtsov is becoming a symbol of our struggle," he said. "Authorities did not allow us to march to the bridge, because they are afraid of a symbolism of Boris's murder place. But we already call the bridge after him, we call it "Nemtsov Bridge" and we will succeed in mounting a memorial plaque at the scene of Boris's murder."
Memorials often removed
Kremlin supporters frequently remove the flowers and break the portraits – attacks that volunteers say are sometimes aided by nearby police.
“The assassination of Nemtsov is not solved,” Kasyanov said earlier in the week. “Only the perpetrators were found, not the paymasters and the organizers of this defiant crime.”
WATCH: Russian opposition leaders targeted year after Nemtsov's assassination
Russian opposition leaders and supporters say that even if President Vladimir Putin was not directly involved in Nemtsov's killing, he bears responsibility for encouraging a truculent authoritarianism.
Opposition leader Ilya Yashin said that Nemtsov’s killing was a terrorist act aimed at threatening those who disagree with Putin’s politics.
"Nemtsov's murder is a terrorist act, it is a demonstrative murder aimed at frightening the Russian society, at least the part which disagrees with Putin's politics. And it is very important for us to demonstrate terrorists, murderers, those villains that they will not succeed in trying to intimidate us."
Moment of silence refused
On the eve of the anniversary, one of the few independent lawmakers in the Russian parliament's lower house, the Duma, proposes that deputies observe a moment of silence in Nemtsov's memory but the majority refused.
Nemtsov, who was a former deputy prime minister during Boris Yeltsin’s presidency and became a fierce critic of Putin, was shot in the back shortly before midnight on February 27, 2015, as he walked across the bridge with a companion.
Trial set for later this year
Several Chechen men were arrested shortly after the murder, including five people who are due to go on trial later this year.
The suspected killer served as an officer in the security forces of the Moscow-backed Chechen leader, Ramzan Kadyrov.
The official investigation has not identified those who ordered the killing. Some Russian opposition activists have criticized the Kremlin for its failure to track down the mastermind.
Earlier this week, Yashin released a report accusing Kadyrov of involvement in Nemtsov's killing and demanded his resignation.
Kadyrov, whose term expires in early April, rejected the accusations.
Putin has relied on Kadyrov to stabilize Chechnya after two separatist wars, making him effectively immune from federal controls.