French anti-terror police are on high alert after a chief rabbi was sent harrowing images of Jewish children being marched to a Second World War death camp.

A menacing letter and the grim pictures were posted to Chief Rabbi Richard Wertenschlag at his synagogue in Lyon.

The letter read: “More and more frequently we are having ideas imposed on us that have as their goal to apologise for the Jew, the so-called Shoah, the evil Palestinians. From now on we will punish a Jew each time that you go on television to complain.”

On the photographs, the letter said: “These prove that the Jews were well treated in Germany, fed and lodged with summer camp for the children.”

Rabbi Wertenschlag said it was not unusual to receive antisemitic mail, but he alerted police to this letter posted earlier this month because of its “threatening and offensive content”.

A Lyon police spokesman said: “We could brush it off as the work of one rogue individual but we have to envisage the worst scenario.”