Russian opposition supporters carry photos of Boris Nemtsov in Moscow | SERGEI GAPON/AFP/Getty
Opposition activist and former Russian Prime Minister Mikhail Kasyanov participates in the rally mourning Nemtsov. | ALEXANDER UTKIN/AFP/Getty
The Cathedral of St Basil, on Red Square, is visible behind the marchers in Moscow | SERGEI GAPON/AFP/Getty
Placards of Nemtsov | YURI KADOBNOV/AFP/Getty
A woman holds flowers at the site where Nemtsov was shot to death, in view of the Cathedral of St Basil. | Sefa Karacan/Anadolu Agency/Getty
DMITRY SEREBRYAKOV/AFP/Getty
Ralliers carry a banner reading "Heroes never die — these bullets are in each of us" | SERGEI GAPON/AFP/Getty
Police stand guard in Moscow | YURI KADOBNOV/AFP/Getty
Flowers laid by supporters rest at the spot where Nemtsov was shot to death. | Sefa Karacan/Anadolu Agency/Getty
St. Petersburg
Thousands also marched in Saint Petersburg, Russia's second-largest city. Police have estimated that 6,000 people attended.
Ralliers carry a banner reading, "Boris Nemtsov, don't forget, don't forgive" | OLGA MALTSEVA/AFP/Getty
Sergey Mihailicenko/Anadolu Agency/Getty
Sergey Mihailicenko/Anadolu Agency/Getty
Sergey Mihailicenko/Anadolu Agency/Getty
Riot police stand guard as ralliers march past. | Sergey Mihailicenko/Anadolu Agency/Getty
A woman holds a portrait of Nemtsov amid Sunday's rally. | Sergey Mihailicenko/Anadolu Agency/Getty
Ralliers carry the flags of Russia, Ukraine (blue and yellow), Saint Petersburg (red), and the political party Yabloko. | Sergey Mihailicenko/Anadolu Agency/Getty
Ralliers hold signs reading "The sleep of reason produces monsters" and "Freedom to Savchenko - You can not afford two heroes." Nadiya Savchenko is a Ukrainian pilot who was captured by pro-Russia rebels and is currently on hunger strike in a Russian prison. | Sergey Mihailicenko/Anadolu Agency/Getty
OLGA MALTSEVA/AFP/Getty
Kiev
Small crowds of supporters have also gathered in the Ukrainian capital of Kiev. Nemtsov was critical of Russia's annexation of Crimea and its military involvement in eastern Ukraine. His position was deeply unpopular in Russia, but appreciated in Ukraine, where he was viewed as a politician sympathetic to Ukraine and a contrast with Putin's policies of exerting control over Kiev. Ukrainian President Petro Poroshenko called him "a bridge between Ukraine and Russia."
Mourners cross themselves at a ceremony for Boris Nemtsov in Kiev's Independence Squara. Former Ukrainian Prime Minister Yulia Tymoshenko stands at center. | SERGEI SUPINSKY/AFP/Getty
Supporters lay flowers for Nemtsov at the Russian embassy in Kiev on Saturday | Vladimir Shtanko/Anadolu Agency/Getty
A man in a Putin mask and a Nazi SS uniform carries a sign reading "Bloody Putin" | SERGEI SUPINSKY/AFP/Getty