People in Moscow and elsewhere in Russia are due on February 29 to pay tribute to Boris Nemtsov -- the former opposition politician and vocal critic of President Vladimir Putin -- who was killed five years ago near the Kremlin.
A march starting around noon through the Russian capital has been approved by Moscow authorities.
A rally to commemorate Nemtsov has also been approved in Russia's second city, St. Petersburg. Commemorations are also expected in Nizhny Novgorod, capital of the region Nemtsov governed in the 1990s.
Some opposition supporters have said they plan to use the event to also protest proposed amendments to the country's constitution. Critics say the planned changes are aimed at extending Putin's grip on power after his current presidential term ends in 2024.
Nemtsov was shot dead at close range on the Bolshoi Moskvoretsky Bridge, a stone's throw away from the Kremlin in central Moscow, on February 27, 2015.
In June 2017, a Russian court sentenced a former Chechen battalion leader Zaur Dadayev to 20 years in prison for killing Nemtsov.
Four other Chechens were found guilty of involvement in the killing and sentenced to prison terms ranging from 11 to 19 years.
But critics, including relatives and colleagues of Nemtsov, say Russian authorities failed to determine who ordered the killing.
Some have expressed suspicions that the killing was ordered by someone within the inner circles of Putin or Chechen leader Ramzan Kadyrov.
A report from the Organization for Security and Cooperation in Europe (OSCE) on February 20 called for "a new and full investigation" into the Nemtsov slaying.
The report, by the OSCE Parliamentary Assembly's special rapporteur, Margareta Cederfelt, said shortcomings in Russia's original investigation left many questions unanswered.
"His death was a tragedy for Russia and had a strong impact on the political climate, spreading fear and possibly opening up for further attacks and repression," the report said.
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