Moscow summoned the Polish ambassador on Tuesday and demanded an apology from Warsaw for damage done to the Russian embassy. A nationalist march had turned violent on Monday.
Long-simmering tensions between Warsaw and Moscow flared up again on Monday, when far-right Poles marched through the capital, on a holiday marking the regaining of independence in 1918.
The Polish ambassador to Moscow, Wojciech Zajaczkowski, was summoned to the Russian foreign ministry, which demanded an official apology from Poland. Rioters had thrown firecrackers at the Russian embassy in Warsaw. Russia also demanded that those responsible be punished.
Police arrested 72 nationalists linked to the riot, in which 12 policemen and 19 protestors were injured.
In a statement, the Polish Foreign Ministry had already expressed deep regret over the incident and said such behavior deserved "strong condemnation."
"There is no justification for hooliganism," Poland's Foreign Ministry spokesman Marcin Wojciechowski wrote on Twitter.
The march, initially peaceful, attracted nearly 50,000 protesters, many of whom brandished Polish flags and chanted slogans such as "God, honor, fatherland."
Polish police used rubber bullets to break up groups of masked youths on Monday, but the Russian diplomats said "passivity and belated action by the police" were largely to blame.
Russian media said that in addition to firecrackers, rioters threw bottles, stones and rubbish at the embassy and set fire to a police booth nearby.
Relations between Poland and Russia have been strained since the break-up of the Soviet Union in the early 1990s. The integration into the West of post-Communist Poland, an EU and NATO member, is one reason for the tensions.
ng/jr (Reuters, AFP)