The mayor of the Polish city of Gdansk has been seriously injured after being stabbed on stage at the country's biggest charity event, officials say.
Pawel Adamowicz, 53, had to be resuscitated at the scene and was taken to hospital in a critical condition.
The 27-year-old suspect, who has a criminal record, has been detained.
He reportedly shouted that he had been wrongfully imprisoned under the previous government, led by the mayor's former party.
What do we know about the attack?
The incident took place at the finale of the annual Great Orchestra of Christmas Charity event, which was attended by hundreds of people.
Television footage showed the suspect, who was released from prison recently, shouting "Adamowicz is dead" and saying he had been tortured in prison.
Polish media initially reported he had access to the stage using a media badge but this has not been officially confirmed.
Polish President Andrzej Duda said he was informed that "doctors succeeded in reanimating the heart of the seriously injured mayor".
"There is hope but his condition is very difficult," he said on Twitter, calling on people to pray for Mr Adamowicz .
What has the reaction been?
The stabbing, during an event that raises money for children's hospitals, has shocked Poland, the BBC's Adam Easton in Warsaw reports.
Mr Adamowicz is a well-known political figure who has been mayor of Gdansk, a Baltic port city, for 20 years, our correspondent adds.
Moments before the attack, he posted a picture on his Instagram from the stage of the event, where dozens of people were holding white lights.
The popular mayor, a former member of Poland's main opposition Civic Platform party, is seen as a liberal voice and has supported rights for minorities.
Interior Minister Joachim Brudzinski said the attack was "an act of inexplicable barbarism".
Prime Minister Mateusz Morawiecki said on Twitter: "The attack on life and health of Paul Adamowicz is worthy of the highest condemnation."