The law, signed by Ukrainian President Viktor Yanukovych, leaves Ukrainian as the only state language, but it allows public servants and citizens to file official documentation in Russian at government bodies, courts and other state institutions in the regions where more than 10 percent of residents are Russian speakers.
Russian is spoken predominantly in the east and south of the country, while Ukrainian is spoken in western Ukraine. But Ukrainian has picked up across the country since the nation became independent after the 1991 collapse of the Soviet Union.
According to a 2001 census, 68 percent of Ukrainians name Ukrainian their native tongue, while 30 percent said it was Russian. Another census is scheduled for next year.