March to remember murdered Kremlin critic Boris Nemtsov
"We gathered here to demand bringing of Boris Nemtsov's killers to justice, not only its performers but also its organisers and those who ordered it," Ilya Yashin, a Russian opposition activist and an organiser of the march, told Reuters news agency.
"We gathered here to demand political reforms and release of political prisoners."
Police put the number of marchers at 5,000, but a group of voluntary observers said there were more than 15,000 demonstrators.
The authorities blocked off several streets in central Moscow for Sunday's event, sealing in the marchers with metal fencing guarded by police.
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