The bill that Poroshenko signed late Wednesday also bans all movies produced by Russian companies and Russian citizens after 1991 if they "glorify the work of government bodies" of Russia.
Relations between Ukraine and Russia soured in 2014 when Russia annexed Ukraine's Crimean peninsula and threw its support behind separatist rebels in eastern Ukraine.
The fighting between the rebels and government troops there left more than 9,100 dead. Despite the European mediation, a cease-fire in the east barely holds and a political settlement looks like a distant prospect.