Poles have taken to the streets to protest against the fatal stabbing of the mayor of Gdansk – and the polarised political culture many hold responsible.

European Council president Donald Tusk, a Gdansk native, led the main gathering in Poland’s northern port city to remember his late friend, Pawel Adamowicz.

The 53-year-old mayor was stabbed at a charity concert on Sunday evening and died from his injuries on Tuesday. Police are questioning a local 27-year-old man seen in video images storming the stage to stab the mayor multiple times.

Afterwards the man, who has a record of violent assault and psychological problems, said the attack was revenge for being allegedly tortured in prison when Poland was ruled by the mayor’s former party, the Civic Platform (PO).

Party co-founder Mr Tusk paid tribute to Mr Adamowicz, his friend from the days of the Solidarity movement, which was founded in their home city and helped collapse Polish communist rule.

“My dear Pawel, you had to wait for such a tragic moment to see from up there just how many friends you have here in Gdansk,” said Mr Tusk to the crowd on Monday evening. “You were always there to show an open and courageous face, and to stand against evil.”

At the Gdansk gathering – and at other spontaneous demonstrations across the country – one subject dominated: the hate speech and toxic nationalism that now saturates Polish political debate.

‘Divisive and polarised’

“It’s hard to describe the mood, this feels like part of Poland’s culture war,” said Paul McNamara, an Athenry native living near Gdansk. “The last decade’s politics has been extremely divisive and polarised people. I don’t want to say this is the inevitable result but . . . ”

Mr Adamowicz’s funeral, likely to be on Saturday, will be an emotional stand-off between the late mayor’s family, supporters and ex-PO colleagues with rivals from the ruling national conservative Law and Justice (PiS) party.

For years PiS has launched sustained attacks on Gdansk, a liberal PO stronghold, and its late mayor, a vocal supporter of migrant rights and the LGBT and Jewish communities. Two years ago an extreme nationalist youth group issued him with a “death certificate”.

Those attacks sit uncomfortably with Sunday’s attack at the Great Orchestra of Christmas Charity (WOSP). Like the mayor, it has faced sustained attacks from PiS and its allies, who suggested patriotic Poles should donate instead to the church and its charities, not a privately run telethon.

After PiS took office, and control of state-owned broadcaster TVP, the charity event vanished from its television schedule.

In its place: regular TVP attacks on the WOSP charity and its founder, ex-rock musician Jerzy Owsiak, including cartoons insinuating financial irregularities and links to unnamed Jewish organisations.

Mr Owsiak has dismissed as “defamation” the last of the attack cartoons, aired a day before the stabbing. He has left the charity, accusing police of failing to take seriously threats that “bordered on the language of Nazism, of fascism”.

2010 air crash

“People are imbibing this vitriol against the charity on TVP, then the mayor shows up at its event and that sets off someone with a five-inch blade,” said Michal, a Gdansk student at the demonstration.

The killing is a new low point in modern Poland and the uneasy post-communist consensus that began to crack with the death of Pope St John Paul II in 2005. After a 2010 air crash killed President Lech Kaczynski, his surviving twin brother Jaroslaw, co-founder of PiS, dismissed reports blaming pilot error and poor weather.

He has framed the crash instead as a conspiracy hatched by his rival Donald Tusk, then PO leader and prime minister, and Russian authorities.

Sunday’s death of his friend appears to have strengthened Mr Tusk’s resolve to return from Brussels and oust PiS from power. He promised to “defend Gdansk and Poland against hatred and contempt”.

Meanwhile, President Andrzej Duda, a PiS ally, has dropped plans for a silent march amid accusations of politicising the tragedy. Instead he urged Poles to “examine our consciences”.

And the late mayor’s last words at Sunday’s concert have gone viral on social media.

“Gdansk is generous, a city of solidarity,” he said. “It’s a wonderful time to share with each other.”