Pro-Palestinian protesters interrupted the Philadelphia Orchestra's Thursday night performance in Brussels, urging the orchestra to cancel the upcoming Israel leg of its tour.

The protesters broke into a performance of the Brahms Piano Concerto No. 1 in D Minor with chants of "free, free, Palestine," and after about 30 seconds, music director Yannick Nézet-Séguin stopped conducting and the music came to a halt, said cellist John Koen. Security removed the protesters, and the concert resumed about 25 minutes later, he said.

An orchestra spokeswoman said she was unsure of the number of protesters, but she believes two were removed from the hall.

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This concert at the Palais des Beaux-Arts de Bruxelles was the first performance of the orchestra’s annual tour that will take the ensemble through several European cities, and them on to Haifa, Tel Aviv, and Jerusalem the first week in June. The trip has also garnered criticism from pro-Palestinian activists locally for what is perceived to be the orchestra’s support of Israel, with several weeks of protests that started in front of the orchestra’s home in the Kimmel Center.

After the interruption, the rest of the concerto with pianist Hélène Grimaud continued without incident.

Nézet-Séguin addressed the audience afterward, telling them that “we are musicians, not politicians, so we use music rather than words,” according to Koen. “Please take the Elgar Salut d’Amour as our gift to you for coming to our concert.”

The orchestra leadership said it would be assessing next steps. "We're in talks with the other presenters [in the other cities on the tour] to speak about security measures that might be taken," said orchestra spokeswoman Ashley Berke.