Foreign diplomats have placed flowers on the Moscow bridge where opposition politician Boris Nemtsov was fatally shot four years ago.
U.S. Ambassador to Russia Jon Huntsman and the ambassadors of several European countries were among the diplomats marking the anniversary of Nemtsov’s killing on February 27.
The United States on February 26 reiterated its call on President Vladimir Putin's government to "identify publicly those who organized and ordered the crime, and hold them accountable."
A liberal politician who was a deputy prime minister during Boris Yeltsin's presidency and became one of Putin's most prominent opponents, Nemtsov was gunned down on a bridge near the Kremlin in Moscow on February 27, 2015. He was 55 years old.
In July 2017, a Moscow court found five men from Russia's North Caucasus region of Chechnya guilty of Nemtsov's murder and sentenced them to long prison terms.
Relatives and associates believe his killing was ordered at a higher level and say justice will not be served until the person or people behind it are identified and prosecuted. The U.S. statement echoed that idea.
Government critics have voiced suspicion that the culprits will never face justice because an honest investigation could lead to figures who are close to Moscow-backed Chechen leader Ramzan Kadyrov or to Putin's inner circle.
Thousands of Russians marched in Moscow, St. Petersburg, and other cities on February 24 to honor Nemtsov, with many criticizing Putin's government and calling for a reversal of what Kremlin critics say has been a clampdown on civil society and dissent since he came to power nearly 20 years ago.
On February 27, at 23:31 p.m. Moscow time, dozens of people gathered at the site of the murder and observed a minute's silence in Nemtsov's memory.
In a statement, the U.S. State Department said that Nemtsov "remains an inspiration to all those in Russia and around the world who strive for justice, democracy, and a government accountable to the people."
The State Department said the United States honors Nemtsov's memory "by renewing our call for the government of Russia to allow journalists, civil society activists, and political opposition members to exercise their universal human rights of freedom of expression, association, and peaceful assembly without fear of violence or other forms of reprisal."