The Glyndebourne festival has defended its production of a children's opera based on the writings of pro-Palestinian American activist Rachel Corrie, killed in Gaza in 2003.

When I Am Old was performed three times last month by members of the Glyndebourne Youth Opera after they spent five days learning about the Middle East conflict.

Organisers said they wanted to show "the courage and idealism of youth" in the opera, performed at the East Sussex venue on Tuesday last week and twice at the Tête à Tête Festival earlier in August.

Ms Corrie, a 23-year-old member of the International Solidarity Movement, was killed in March 2003 as she attempted to block IDF bulldozers clearing an area used by terrorists to dig tunnels under the border with Egypt.

In When I Am Old, children acting as IDF soldiers shout through megaphones and jostle audience members. They then, according to the libretto,"shoot their guns into the air for fun," after forcing Palestinian characters out of their homes.

One soldier sings: "There is no such thing as a civilian in a war zone."

In a later scene an affluent couple are seen discussing their plans for the day before catching a bus which then blows up, the target of an apparent suicide bombing. The performance concludes with a recitation based on Ms Corrie's writings about ageing.

Around 20 young singers, aged between 13 and 21, take part in the opera, composed by Hannah Conway, and part-funded by former Guardian journalist Linda Christmas.

At last week's performance, the audience of around 200 people was handed a director's note written by Karen Gillingham, explaining: "The Rachel Corrie story affected us deeply and we were all left with an overwhelming feeling of wanting to know why and how this had happened. Amy Doust, our adviser on the Middle East, gave us an invaluable insight into the world that Rachel found herself passionately part of."

Glyndebourne fan Ian Harris attended the opera and said: "I just could not believe what I was seeing. It was an outrageous, totally one-sided piece of anti-Israel propaganda, which Glyndebourne, with its many Jewish patrons and supporters, should never have allowed. It portrayed Israeli soldiers as callous child-murderers.

"The performance was disgusting, not least because of the effect of this propaganda on its young participants." Mr Harris has complained to Gus Christie, executive chairman of Glyndebourne.

A Glyndebourne spokeswoman said: "We were particularly careful in the five-day development workshops in February with the youth opera that they explored the history of the conflict in the Middle East, so that the young people involved were given a balanced picture."

Ms Corrie's parents are pursuing a civil case against the state of Israel. They claim that an inquiry into her death was not comprehensive enough and that their daughter's death was intentional.