Updated at 3.10pm - Mayor succumbs to injuries

A knife-wielding assailant stabbed the mayor of the Polish port city of Gdansk in front of hundreds of people at a charity event on Sunday evening.

The mayor, who spent five hours in surgery, succumbed to his injuries on Monday. 

Video footage showed the attacker bursting onto the podium and launching himself at Pawel Adamowicz, 53, who had been waving sparklers with others on stage at the Sunday evening fundraiser.

After knifing the mayor several times, the man turned to the crowd with his arms raised triumphantly but was quickly tackled to the ground by security guards and arrested.

Paramedics resuscitated Adamowicz at the scene before rushing him to hospital for surgery. 

The mayor suffered a serious wound to the heart and cuts to the diaphragm and abdominal organs, said Tomasz Stefaniak, the surgeon who treated him at Gdansk's university hospital.

He subsequently succumbed to his wounds. 

"Despite all our efforts, we failed to save him," Dr Stefaniak, said, quoted by the Polish PAP news agency.

A local police spokesman said the detained man was a 27-year-old who lived in Gdansk, a Baltic coast city with a population of around half a million.

In a video recording of the attack posted on YouTube, the suspect was seen seizing the microphone and claiming he had been wrongly jailed by the previous centrist government of the Civic Platform (PO) and tortured.

"That's why Adamowicz dies," he said.

One eyewitness told broadcaster TVN that the man appeared "happy with what he had done".

'Press' badge 

Adamowicz was mayor of Gdansk for two decades and the Civic Platform had supported his re-election in 2018 municipal polls.

Sunday's event was part of a big nationwide drive to raise funds for the purchase of medical equipment and featured a colourful stage set-up including lights, smoke and pyrotechnics.

"There is hope but his condition remains serious," Polish President Andrzej Duda had said on Twitter following the attack.

"Despite our political differences, I stand without question in solidarity with him and those close to him... I pray for his swift recovery," the leader said.

According to local media, the suspect had been sentenced to more than five years in prison for four armed attacks on banks in Gdansk.

His mental state had severely deteriorated during his time in jail, reports said.

Police were investigating how the attacker had been able to breach security to reach the podium, local police spokeswoman Joanna Kowalik-Kosinska told reporters.

"We know that he used an identifier with the inscription 'Press'," she said. "Now we have to establish how was it obtained, was the accreditation in his name and was he really entitled to be there at that time?"

Polish Prime Minister Mateusz Morawiecki condemned the attack on Twitter and Interior Minister Joachim Brudzinski called it "an incomprehensible act of barbarism".

Overseas officials including EU President Donald Tusk, European Commission Vice President Frans Timmermans and mayor of London Sadiq Khan also expressed their support for Adamowicz.