Police have arrested 23 people who took part in a sit-in demonstration at Radboud University in Nijmegen calling for the university to sever ties with Israeli institutions.

The protest at the Goudsmitpaviljoen, a physics laboratory on Heyendaalseweg began on Tuesday evening and continued until the early hours of Wednesday. An ultimatum to leave the building expired just after 9pm.

University authorities said the occupation was a security risk because the building, part of the science faculty, houses superconducting magnets and refrigerating gases.

Demonstrators were arrested as they left the building over the course of the night. Riot police and a team from the explosives specialist unit EOD were on standby but were not called into action.

City mayor Hubert Bruls said: “Despite repeated warnings, the occupiers remained in the building, which was life-threatening behaviour.”

Organisers Nijmegen Student Encampment had vowed to continue the occupation until the university ended its partnerships with Israel. Radboud suspended its co-operation with Tel Aviv University and the Hebrew University in May because of what it described as “human rights violations in the Palestinian territories”.

But the protesters accused the university of “supporting genocide”. A spokesman said: ”This building is part of the co-operation between Israel and Radboud University. We are here to prevent that.”

The campaaign group said the occupiers had not done anything to endanger the safety of the building or those inside. “We are observing the security rules and have the situation under control,” the spokesman said.

But faculty dean Sijbrand de Jong said the contents of the building were highly explosive and required “very specific knowledge”. “I don’t know what kind of expertise they have, because all the experts are out here,” he said.