Polish blood donors have massed Monday to try to save the life of the mayor of Gdansk, who needs transfusions after stabbing the heart and abdomen at a charity event.

The doctors operated for five hours on Mayor Pawel Adamowicz, stabbed Sunday by a former convict who rushed to the scene with a knife, launched the attack and shouted that he was in danger. It was a political revenge against a political party to which Adamowicz belonged.

Adamowicz grabbed his belly and collapsed in front of the public during the 27th annual fundraiser organized by the Grand Orchestra of Christmas Charity.

Doctors resuscitated Adamowicz on the spot, then took him to the Gdansk Medical University, where he was operated for five hours.

One of the surgeons, Dr. Tomasz Stefaniak, said that Adamowicz was in a "very, very serious condition" after suffering a "serious heart injury, an injury to the diaphragm and internal organs". He added that Adamowicz needed massive blood transfusions.

He said the next few hours would be decisive and asked for ideas and prayers from the mayor who has been sitting since 1998.

Private TVN24 on Monday showed people lining up and donating blood to Gdansk. Some said that they had free time to help save Adamowicz. A rally against violence was also planned.

The Archbishop of Gdansk Leszek Slawoj Glodz, who was in the hospital during the operation, said that he was praying for a "miracle".

After the knife attack, the assailant shouted that he had been wrongfully imprisoned under a previous national government led by Civic Platform, a party to which the mayor previously belonged. He said that he called Stefan and that "I was imprisoned but innocent … Civic Platform has tortured me … that's why Adamowicz just died." "

Police said the suspect was a 27-year-old man who had just been released from a prison where he had served a sentence for robberies at a bank. A police spokesman, Mariusz Ciarka, said that the attacker appeared to be suffering from mental problems and that he had been able to enter the area with a badge. We did not know how he acquired the title.

He has been arrested and is currently the subject of an investigation.

The TVN footage showed Adamowicz on stage with a sparkler in his hand, telling the audience that the day had been "wonderful", and then the attacker went to him. The mayor had already made his way to the streets of his Baltic port city earlier in the day to raise funds for a national charity supporting Polish hospitals facing financial difficulties.

The President of the European Council, Donald Tusk, former Polish Prime Minister and co-founder of Civil Platform from Gdansk, tweeted: "Let's all pray for Mayor Adamowicz, Pawel, we are with you."

The head of the association, Jerzy Owsiak, is a liberal critic of the current right-wing government in Poland. Owsiak and some opposition politicians blamed the attack on what they described as an atmosphere of hate under the ruling party, the ruling party, Law and Justice.

Adamowicz, 53, was part of the democratic opposition formed in Gdansk under the leadership of Lech Walesa in the 1980s. After leaving Civic Platform, he was re-elected for a sixth term as an independent candidate for the 39; fall.

As Mayor, he has been a progressive advocate, defender of LGBT rights and tolerance of minorities. He participated in the gay pride parade last year, a rare action for a mayor in Poland.

He also showed solidarity with the Jewish community when the city's synagogue had broken windows last year, strongly denouncing vandalism.

"Horrified by the brutal attack on the mayor of Gdansk, Pawel Adamowicz," tweeted Frans Timmermans, a Dutch politician and senior official of the European Union. "I hope and pray that he recovers, a great leader of his city and a true humanitarian."

The last attack against a politician in Poland took place in 2010 in Lodz. A man shouting that he wanted to kill the leader of the "Law and Justice" party, Jaroslaw Kaczynski, shot dead an assistant to one of the party's legislators in the European Parliament. A second man was stabbed and injured.

At the time, Law and Justice were in opposition and Kaczynski blamed the attack on an "atmosphere of hate" under the regime of the rival civic platform.