Russia's Foreign Ministry says Moscow has expelled a Ukrainian diplomat in retaliation for Kyiv's expulsion of a Russian diplomat.
Few other details were immediately available from the Russian news reports on September 1.
Ties between Moscow and Kyiv hit rock bottom after Russia annexed Ukraine's Crimea Peninsula in March 2014.
Unrest then started in Ukraine's Russian-speaking east. Kyiv and the West accuse Moscow of driving a separatist rebellion there. Moscow denies that.