About 100 people, including several prominent opposition leaders, have been detained during a demonstration in the Russian capital, police said.
Moscow police spokesman Viktor Biryukov said about 300 people gathered on Triumphalnaya Square Sunday in anti-Kremlin protest.
Boris Nemtsov, former Russian deputy prime minister, Eduard Limonov, leader of opposition movement The Other Russia and Oleg Orlov, head of the Memorial human rights group, were among the protestors.
"After repeated requests to stop the rally, police detained about 100 people, including Boris Nemtsov, Eduard Limonov and Oleg Orlov," he said.
The protesters said they gathered to show the authorities are violating the Russian Constitution, which grants the right to assemble peacefully.
Nemtsov, who served as deputy premier from 1997 to 1998, is a leading member of Russia's political opposition and is known for his criticism of Prime Minister Vladimir Putin's policies.