As of Monday, Russian citizens traveling to Ukraine will be limited to a stay of no longer than 90 days within a six-month period.
Russian citizens visiting Ukraine could previously stay for a period of three months, after which they were able to "renew" their legal 90-day stay by simply crossing the Russian border and coming back, the Ukrainian border guard administration said, RIA Novosti reported.
However, from Monday, border guards will to be on the lookout to see if Russian citizens are abiding by the new restrictions.
Andrei Sibiga, head of the Ukrainian Foreign Ministry's consular department, said Ukrainians traveling to Russia faced the same level of restrictions at the start of the year.
Relations between Kiev and Moscow have soured in recent months, following the ousting of Ukraine's pro-Russian President Viktor Yanukovych in February and Russia's annexation of the Crimean peninsula in March.