Russia has banned all dairy imports from Ukraine, citing a lack of quality control.
The move is the latest sign of worsening trade relations between the two countries after Ukraine signed a free-trade pact with the European Union.
A spokesman for Russia's food and agricultural inspection service, Rosselkhoznadzor, said the ban was imposed after high levels of antibiotics and bacteria were detected in Ukrainian dairy products.
The ban comes into effect on July 28.
Russia has previously imposed import bans on countries seeking to move closer to the European Union and away from Moscow.
Earlier this month, Russia banned meat and fruit imports from Moldova, which also signed an EU Association Agreement in June.