Protests continue to roil several European universities, including in Portugal, as students confront their administrations over Israel, urging them to sever or drastically reduce ties with the Jewish state.

In the Netherlands, officials at the nearly 400-year-old University of Amsterdam said in a statement that they could no longer guarantee anyone’s safety on campus after a group of masked protesters barricaded doors and spray-painted slogans on walls.

Monday’s mayhem followed a peaceful strike by staff and students over the war between Israel and Hamas in the Gaza Strip and the university’s response to earlier protests.

“They [the university] called the police because people didn’t want to show their faces, but the police came in full riot gear,” Enzo Rossi, a political science professor, told The Associated Press, describing Monday’s events.

Rossi also alleged that he and his wife, who also works for the university, were repeatedly hit by police with batons.

Last week, police used an excavator to remove protesters from a tent camp set up by students who want the university to cut ties with Israel.

Smaller anti-war demonstrations have taken place at the University of Amsterdam and other Dutch universities.

Riot police have been called in several times to break up the demonstrations, leading to clashes.

After Monday’s violence, some students set up tents inside campus buildings, vowing to occupy the spaces until the university meets their demands.

The University of Amsterdam said the peaceful protest was “hijacked by violent elements” who left behind “wanton destruction.”

Higher education institutions in the Netherlands on Tuesday issued guidelines for student protests, including a ban on overnight stays, building occupations and face coverings.

Last week, the University of Amsterdam said it would not hold talks with any demonstrators who refused to show their faces.

The current Gaza conflict was triggered by an unprecedented rocket barrage by the Palestinian militant group Hamas on Oct. 7, 2023, that killed about 1,200 people and took two Israelis hostage, according to Israeli authorities.

In response, Israel launched an offensive that has killed more than 35,000 people and wounded 79,000, according to Hamas, which has controlled the Palestinian enclave since 2007.

Read Also: Universidade de Amesterdão encerra dois dias após protestos pró-Palestina (Portuguese version)