Thousands of protesters marched through Moscow on Saturday against the Russian government’s proposed constitutional changes that are widely seen as an attempt by President Vladimir Putin to maintain his power beyond the end of his term in 2024.

Police said some 10,000 people took part in the march, while a nongovernmental organization that has counted attendance at political rallies estimated a turnout of 22,000.

Protesters could be seen carrying placards with sayings such as "No to eternal Putin" and "No to the usurpation of power."

Other marchers held signs commemorating Boris Nemtsov, a charismatic opposition leader who was murdered five years ago while walking on a bridge near the Kremlin.

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An officer in the security forces of Chechnya's Kremlin-backed leader was sentenced to 20 years in prison for firing the shots that killed Nemtsov. Four other men were sentenced 11 to 19 years for involvement in the slaying, but whoever organized and ordered the assassination has not been determined.

Demonstrations in Nemtsov's memory also took place Saturday in other large cities across Russia, including St. Petersburg, where about 2,000 people gathered, and in Novosibirsk and Vladivostok.

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Officials with the arrest-monitoring organization OVD-Info said police detained five demonstrators in St. Petersburg, but there was no immediate information on charges. No detentions were reported in the Moscow march.

The Associated Press contributed to this report.