“We thought we’d liven up the Webern a bit,” Ms. Fink was quoted as saying. “The performance of Beethoven’s Ninth Symphony at the previous night’s Prom was so exciting that we decided to treat the audience to our own version of the ‘Ode to Joy.’ ” She then cited lines from the protesters’ bitterly satirical version of the 18th-century poem by Friedrich Schiller that is sung to Beethoven’s score:

Israel, end your occupation:

There’s no peace on stolen land.

We’ll sing out for liberation

Till you hear and understand.

Several concertgoers said that the audience appeared to be overwhelmingly hostile to the protesters, with boos, shouts and cries of “Shut up!” countering the protesters’ choruses.

“It was just quite upsetting,” said Tom Dixon, one of the concertgoers. “The Israelis had come just to play music, and they were being targeted for something I don’t think they were involved in at all.”

Another man in the hall, Jonathan Hoffman, said he had carried an Israeli flag to the concert and waved it during the protests. “I’m proud of the fact that I’m Jewish,” he said. “I’m proud of this wonderful orchestra that consists of people who face terror every day.”

Ms. Driver, the Proms spokeswoman, said the police officers who had been posted at the entrances to keep peace between pro-Israeli and pro-Palestinian protesters did not enter the hall, and made no arrests.

She said that concerns about possible disruption inside the hall had prompted the organizers to mount an unusually thorough search of all the concertgoers, but that the checks had not discovered the patches of hand-lettered cloth that protesters inside the hall had used to spell out the words “Free Palestine” as they staged their demonstrations.

BBC Radio Three, the highbrow station that broadcasts the Proms, cut away quickly after the first of the protests broke out, apologizing to listeners for the interruption. It returned twice to the concert, resuming the broadcast, before finally abandoning it.

During the breaks, and after the final interruption, the station played recorded versions of the works on the orchestra’s program. In the concert hall, Mr. Mehta led the orchestra through the full program, concluding to a huge ovation and an encore.