Eduard Limonov, a radical leftist writer and founder of the National Bolshevik Party, was among the people arrested at Triumfalnaya Square as they defended the constitutional right to assembly.

Moscow police spokesman Viktor Biriukov said 50 people were detained, according to Interfax.

Human rights activist Lyudmila Alexeyeva, one of the recipients of the European Parliament’s prestigious Sakharov Prize this year, was blocked from reaching the demonstration as a security agent followed her every move.

Alexeyeva, 82, was wearing an apron that read, “Respect the Constitution”.

Tatiana Kadieva, a member of the United Citizen Front of chess master Garry Kasparov, said the opposition would meet on the last day of every month “as long as we are not allowed to assemble freely.”