Russia will take steps to respond after Latvia made it harder for Russian citizens to extend residence permits, foreign ministry spokeswoman Maria Zakharova told the RIA news agency on Thursday.
Moscow would "continue to take tough measures, including those of asymmetric nature", Zakharova added, but gave no examples of possible steps.
She said Riga's moves, which include requiring a Latvian language test for Russians seeking to renew the permits, were arbitrary and contradicted a number of human rights treaties.
