Polish President Bronislaw Komorowski on Sunday was struck by an egg hurled by a young man during a sensitive visit to Ukraine to commemorate a wartime massacre, police said.
The man went up to Komorowski as he was talking to people at a ceremony in the northwestern city of Lutsk to mark the 70th anniversary of the killings of tens of thousands of Poles by Ukrainian nationalists during World War II.
The attacker broke the egg on Komorowski's shoulder, said police from the Volhynia region, where the ceremony took place.
However, the Polish president was not hurt.
"The attacker has been arrested. Now his identity and the motives that would have caused him to do such a thing are being investigated," a police spokesman said.