Thousands of people in cities across Poland have joined anti-violence rallies to protest the stabbing murder of the popular mayor of the city of Gdansk, who advocated refugee rights.

Mayor Pawel Adamowicz succumbed to his injuries early on Monday afternoon after being stabbed in the chest Sunday evening by a recently-released former prison inmate while on stage for a charity Christmas concert.

Thousands gathered in cities across the Eastern European country a day after the stabbing of the veteran mayor of Gdansk to protest what some local observers see as the creeping of hate speech into the national discourse of Poland, which is currently being ruled by a right-wing, anti-refugee government.

Thousands also converged at Gdansk’s statue of Neptune in the city’s Long Market — which also houses the city hall, where Adamowicz served as mayor for more than 20 years — as European Council President Donald Tusk, a Gdansk native and longtime ally of the mayor, addressed the crowd.

“My dear Pawel, we are here with you today as your friends. You had to wait so long, until such a tragic moment, to see from up there just how many friends you have here in Gdansk,” Tusk said during an emotional speech.

According to local press reports, Adamowicz had long been the target of hate in Poland’s far-right circles for his liberal views and vigorous defense of refugees, though there is no firm proof yet that the fatal stabbing was politically motivated.

Moreover, some in the country are also blaming the attack on a more general surge of social tensions and a growing prevalence of hate speech, insisting that even before Adamowicz’s death, silent protest gatherings had been planned in a number of Polish cities on Monday.

In Gdansk, the city flag was lowered to half-mast, and a mass was planned for later on Tuesday as the assassination of the six-term mayor — who reportedly often mingled freely with the citizens of his city — sent shock waves throughout Poland.

Politicians from across the country’s political spectrum censured the assassination, including Prime Minister Mateusz Morawiecki, Interior Minister Joachim Brudzinski, and other members of the ruling nationalist Law and Justice Party (PiS), which Adamowicz had opposed.

Adamowicz was part of the democratic opposition established in Gdansk under the leadership of former Solidarity labor leader, Lech Walesa, during the 1980s. He re-elected for a sixth term as an independent candidate late last year.

He died on Monday after undergoing more than five hours of surgery on Sunday night. The assailant was identified only as a 27-year-old man named Stefan, with his full name being withheld. He is reportedly from Gdansk and was released from prison last month.

After the stabbing, the attacker grabbed the microphone on the stage and told the crowd he blamed Adamowicz’s former political party, Civic Platform, for his jailing and alleged torture in 2014 for a series of violent attacks.

Death threat against president leads to arrest

Meanwhile, Polish police officers have taken into custody a man who made death threats against President Andrzej Duda on Monday, said an official police statement posted in a Twitter message.

According to the statement, a 72-year-old resident of Warsaw was detained after he called a local Family Assistance Center and made threats against the president, saying, “Adamowicz died and Andrzej Duda may die tomorrow.”