Russia on Saturday promised it would respond harshly to Poland's "seizure" of its embassy school in Warsaw, an act it called a "blatant violation" of the Vienna Convention on diplomatic relations.
Russia's RIA news agency had earlier reported that the Polish authorities, accompanied by police, broke into a school run by the Russian embassy in Warsaw and padlocked the gate.
When asked about the incident, a Polish Foreign Ministry spokesperson told Reuters the building housing the embassy school belonged to the Polish state.
The Russian Foreign Ministry said in a statement that the Polish authorities had burst onto the embassy school's grounds with the aim of seizing it.
"Such an insolent step by Warsaw, which goes beyond the framework of civilised inter-state relations, will not remain without a harsh reaction and consequences for the Polish authorities and Polish interests in Russia," the ministry said.
(With input from Reuters)