Nemtsov was shot and killed by unknown gunmen in central Moscow, next to St. Basil's Cathedral, late Friday night. Investigators are considering several theories, including a possible contract killing.
According to the authorities, at least 7,000 people are marching past Nemtsov's murder site just outside the Kremlin. Many are carrying portraits of the slain politician, flowers and mourning ribbons, as well as flags of Nemtsov's liberal RPR-PARNAS party.
Initially, an opposition rally, with Nemtsov being one of the organizers, was scheduled for Sunday in southern Moscow. Following the politician’s murder, the rally was turned into a commemoration march and moved to the city center.
The march has been approved by Moscow authorities, and is monitored by police, as well as observers from the Russian Presidential Council for Civil society and Human Rights.
Nemtsov served as Russia’s deputy prime minister under the former President Boris Yeltsin in the 1990s. He later turned into one of the most prominent government critics and an active member of Russia’s liberal opposition, co-chairing the RPR-PARNAS party since 2012.