The mayor of the Polish city of Gdansk has died in hospital, a day after being stabbed at a charity event.
Pawel Adamowicz, 53, was attacked on stage in front of hundreds of people on Sunday.
He was taken to hospital for stab injuries and underwent five hours of surgery at a local hospital.
A 27-year-old with a criminal record has been arrested over the attack. Police believe he used a media pass to gain access to the stage.
Poland's health minister on Monday confirmed Mr Adamowicz had died.
"We couldn't win," Lukasz Szumowski told local media, referring to the battle to save his life.
Thousands attended vigils across Polish cities on Monday evening, including in Gdansk.
President Andrzej Duda described the attack as an "evil hard to imagine".
He said the day of the politician's funeral would be observed as a day of national mourning.
How did the attack happen?
The mayor was stabbed on Sunday while attending the Great Orchestra of Christmas charity - an annual event where volunteers raise money for medical equipment in hospitals.
Moments before he was attacked, he posted a picture from the stage on Instagram.
Television footage from the event showed the suspect rushing the stage and stabbing the mayor several times.
He then shouted to the crowd before being tackled to the ground and arrested.
Paramedics tried to resuscitate Mr Adamowicz at the scene, before transferring him to a hospital.
What is known about the suspect?
Polish media say the suspect is a 27-year-old named Stefan - but his full identity has so far been withheld.
A police spokesman said the man had a long criminal history, including a bank robbery and an attack on a police officer.
They also confirmed that he was released from prison late last year.
Police say they are looking into how the suspect was able to breach the event's security.
While on stage, he reportedly shouted "Adamowicz is dead" and said the Civic Platform party, which led the previous government and had supported Mr Adamowicz's re-election as an independent candidate, had wrongfully imprisoned him.
He also alleged he had been tortured behind bars.
The suspect will undergo psychological assessment to see whether he can be held criminally responsible for the attack, prosecutor Krzysztof Sierak said at a press conference on Monday.
Who was the mayor?
Mr Adamowicz was a popular figure - known best for his liberal political views and extensive tenure as mayor.
The father-of-two was from Gdansk and had held the position for two decades.
He first came to power in 1998 - and had been re-elected four times since, including in November.
Doctors said the victim sustained injuries to his heart, as well as cuts to his diaphragm and abdomen.
Surgeons said he was given 41 units of blood during a five-hour operation on Sunday.
After news of the severity of his condition broke, local residents queued at the hospital to donate blood.
What has reaction been?
The BBC's Adam Easton in Warsaw says his murder has left Poland in a state of shock.
Politicians from across the political spectrum have condemned the attack.
On Sunday, Interior Minister Joachim Brudzinski described it as "an act of inexplicable barbarism".
Prime Minister Mateusz Morawiecki described is death as a "huge tragedy" for Poland.
EU Council President Donald Tusk also paid tribute to him in a tweet.
Paweł Adamowicz, Mayor of Gdańsk, a man of Solidarity and freedom, a European, my good friend, has been murdered. May he rest in peace.— Donald Tusk (@eucopresident) January 14, 2019
After news of Mr Adamowicz's death broke, his official Twitter account posted a black-and-white photograph in tribute.
The post was met with dozens of messages of mourning.
Paweł Adamowicz 1965-2019 pic.twitter.com/bGhHj8LwFf— Paweł Adamowicz (@AdamowiczPawel) January 14, 2019
President Duda said he originally planned to organise a march against violence with other politicians in response to the attack, but that on Monday he changed his mind to respect the wishes of the mayor's family.
"Together we came to the conclusion that marches organised by the authorities are not needed in the present situation," he said.
"If citizens want to organise marches, spontaneous marches, then please, they can do it."