Poland's President apologized on Wednesday after far-right protesters threw firecrackers at the Russian embassy in Warsaw, triggering a tit-for-tat attack in Moscow and a heated diplomatic spat.
During Monday's celebrations of Polish Independence Day, police had to use rubber bullets to break up groups of masked far-right youths during an annual march in the center of the capital.
When the march reached the Russian embassy - symbol for some Poles of decades of Soviet domination in the Communist era - some in the crowd threw firecrackers at the building.
“This is an absolutely scandalous event that took place at the Russian embassy. It cannot be excused with anything. One can only deeply apologize,” President Bronislaw Komorowski told Radio Zet.
Russia's Foreign Ministry had summoned the Polish ambassador in Moscow to demand an apology for Monday's violence.
On Wednesday Russian protesters threw firecrackers at the Polish embassy in Moscow.
“Poland is demanding detailed explanations from the Russian side on this matter,” the Polish Foreign Ministry said in a statement.
Russian police detained three men after the incident, which the opposition group Other Russia said was intended as a response to the anti-Russian violence in Warsaw.
Grievances between Warsaw and Moscow go back centuries, and modern-day disputes include mutual recriminations over the 2010 plane crash near the Russian city of Smolensk that killed Poland's President Lech Kaczynski and 95 others.
Since the end of Communist rule in 1989, Poland has pursued close integration with the West and has trade and security disputes with Russia. It joined the European Union in 2004, became a NATO member in 1999 and plans to host part of a NATO missile defense system on its soil, a project opposed by Moscow.