Mayor of the Polish city of Gdansk underwent surgery after being stabbed by an attacker on Sunday, local media reported.
According to Radio Gdansk, Pawel Adamowicz was stabbed in the heart during a charity concert and taken to hospital immediately.
A spokesperson of the hospital told local media that the mayor was in "very, very serious" condition.
Polish broadcaster TVN said a 27-year-old suspect was arrested at the scene. He shouted after the attack that despite being innocent, he was imprisoned and tortured under the government of Civic Platform, a party to which the mayor formerly belonged.