The Russian ambassador to Poland was attacked with red paint by pro-Ukraine activists in Warsaw on Monday when he tried to lay a wreath to mark Victory Day, Russia's foreign ministry said.

Victory Day is celebrated annually on May 9 to commemorate the Soviet defeat of Nazi Germany in World War II. This year's events are taking place as Moscow's military campaign in Ukraine enters its third month.  

"In Warsaw, during the laying of a wreath at the cemetery of Soviet soldiers, an attack was carried out on the Russian ambassador to Poland, Sergei Andreev, and the Russian diplomats accompanying him," foreign ministry spokeswoman Maria Zakharova said on Telegram.

"The admirers of neo-Nazism have again shown their faces," she said, repeating Russia's assertion that it is fighting neo-Nazis in Ukraine.

"But as I have said before, we cannot be intimidated. It must be terrible for the inhabitants of Europe to see their own reflections in the mirror."

Images released by Russian news agencies showed Andreev and several other men with red paint splattered across their clothes and faces, surrounded by a chanting crowd, some holding Ukrainian flags. 

Andreev told Russian news agency RIA Novosti that he was not seriously harmed in the attack.

Poland has accepted hundreds of thousands of refugees from neighbouring Ukraine since Moscow sent troops into the country on February 24.