Prime Minister Mette Frederiksen of Denmark was attacked in a busy square in Copenhagen on Friday evening in an assault that left her “shaken,” her office said, though she was able to walk away. Police said they had made an arrest.

“We have a suspect in custody, and we are now investigating the matter,” the Copenhagen Police said, without commenting further. The motive for the attack is unclear.

The prime minister’s office released a statement saying she had been “beaten,” several media outlets reported, but it was unclear what injuries she had sustained.

Several Danish politicians expressed their concern over the episode.

“Mette is naturally shocked by the assault,” Magnus Heunicke, Denmark’s minister for the environment, wrote on X. “I must say, it shakes all of us who are close to her.”

Ms. Frederiksen, 46, has been prime minister since 2019. She leads the center-left Social Democrats.

The attack came just days before Danes will vote in the European Union elections.

The assault also resonated beyond Denmark’s borders, with the prime ministers of Finland and Sweden sending their support. It happened not even a month after Prime Minister Robert Fico of Slovakia was shot and badly wounded in an assassination attempt he survived.

Ms. Frederiksen was in Normandy on Thursday and gave a speech during commemorations for the 80th anniversary of D-Day. She honored the sacrifices of Danish soldiers and extolled the virtues of freedom, saying: “Freedom is not a legacy. Freedom is a fight, a battle, a struggle. Every day. Every hour. Right now.”

Kaly Soto contributed reporting.