A local leader of the Alternative für Deutschland party has been attacked and injured in the city of Bremen.

Bremen police said they believe the attack on Frank Magnitz, an MP in Germany’s national parliament who leads the party’s local branch, was politically motivated.

They called for witnesses to the attack, which took place early on Monday evening near a city theatre, to come forward.

Mr Magnitz was beaten over the head with an unidentified object by at least three men wearing dark clothing and hoods or hats, who then fled, police said.

Two workers who were loading a car nearby found him lying on the ground and called an ambulance. The 66-year-old was taken to hospital.

Police officers stand in the backyard of the Goetheplatz theater where Frank Magnitz, was attacked in Bremen, Germany. Photograph: Focke Strangmann/EPA

The party, known by its German acronym AfD, said earlier that he was ambushed by three masked men, beaten unconscious with a piece of wood and then kicked in the head.

“It was clearly an attempt to murder Mr Magnitz,” AfD co-leader Alexander Gauland told reporters in Berlin.

“This is the result of the ostracism and agitation AfD faces,” he said, suggesting other parties were partly responsible for the attack because they had compared AfD to the Nazis.

The party claims there have been “hundreds” of attacks against its members since its founding in 2013.

Last week, an explosion outside one of its offices in the eastern town of Döbeln damaged windows and doors.

AfD distributed a photograph of Mr Magnitz lying on a hospital trolley, showing a bloody, gaping wound on his head and his right eye bruised and swollen.

He told the dpa news agency he had been told he would need to remain in hospital until the weekend and had little memory of the attack.

He added that while he had received threats, he had not considered any of them concrete.

He is associated with the right wing of the party, including its firebrand leader in the eastern state of Thuringia, Björn Höcke.

Bremen, Germany’s smallest state, holds a regional election on May 26th, the same day as European Parliament elections in which AfD hopes to make gains.

Foreign minister Heiko Maas, who has been a strong critic of AfD, tweeted: “Violence must never be a means of political confrontation – no matter against whom or what the motives are.”

“There is no justification for this,” he said, calling for those responsible to be punished.

That was echoed by other politicians from established parties, including prominent Green party politician Cem Özdemir, who said that AfD must be countered by legal means, not violence.

“Anyone who fights hatred with hatred always lets hatred win in the end,” he wrote on Twitter.

AfD is represented in all of Germany’s 16 state parliaments. It entered the national parliament in 2017 and is currently the biggest opposition party. – AP