Russia is demanding a formal apology from the Polish authorities after three children of Russian diplomats were attacked in a Warsaw park.
President Putin's condemnation was broadcast on Russian TV
The teenagers are said to have been attacked by 15 youths shouting anti-Russian slogans.
Russian President Vladimir Putin condemned the attack, saying the "unfriendly act" was a crime.
Poland's ambassador to Moscow Stefan Meller was summoned by the foreign ministry after the incident.
He told Echo Moscow radio that "as an ambassador and a Pole I can say I am very sad and that I ask forgiveness from the children".
The Russian foreign ministry has blamed Polish politicians for stirring anti-Russian feeling in the country.
Moscow says the attackers mugged the teenagers, stealing their money and mobile phones. Two of the victims are said to have lost teeth.
Mr Meller said it was an attack by "skinheads against children, not Poles against Russians".
Poland's foreign ministry spokesman Aleksander Checko said Poland "deeply regrets that something like this happened to our guests, the children of Russian diplomats working in Poland".
He said the authorities would do everything "to catch and punish the attackers".