Sergei Udaltsov, leader of the Left Front leftist opposition group, said Saturday that the group submitted a request to Moscow authorities requesting permission for a march Jan. 13.
"The demonstration of 20,000 people will walk from Belorussky train station down to the State Duma," Udaltsov said.
Russian President Vladimir Putin signed the new adoption law Friday, and it will go into effect Jan.1, RIA Novosti reported.
The adoption law was a response to the U.S. Magnitsky Act, which U.S. President Barack Obama signed into law earlier this month, introducing sanctions against Russian officials suspected of human rights abuses, the Russian news agency reported.
Critics of the adoption ban said it will pressure Russian's dilapidated orphanage system with tens of thousands of children who would otherwise be adopted by Americans.
"We consider [the adoption law] antihuman and savage, it's an inadequate reaction to the Magnitsky Act," Udaltsov said.