Michel Valet said he had received a complaint from the school and had ordered a police investigation to discover the "origin of these calls and letters and the identities of those behind them."

The Ozar Hatorah school was at the centre of a national drama on March 19, when self-declared Al-Qaeda operative Mohamed Merah pulled up on his scooter and attacked a crowd of pupils and parents waiting for class.After killing a 30-year-old religious studies teacher and his two sons aged four and five, the 23-year-old Islamic extremist pursued a seven-year-old girl onto the grounds, grabbing her and shooting her through the head.

The local head of a Jewish representative group, Marc Sztulman, said the school's email system had filled up with messages "calling for the murder of Jews or drawing a vague link with the Israeli-Palestinian conflict."On Monday, a 12-year-old Jewish boy was beaten but not badly hurt by three unidentified teenagers in an anti-Semitic attack outside another school in the Ozar Hatorah group, this time in Paris, according to police.

President Nicolas Sarkozy and other national leaders have called for national unity since Merah's attacks, insisting that his crimes do not represent Islam nor France's large Muslim minority.But some figures, notably far-right presidential candidate Marine Le Pen, have linked the attacks to what they see as a too liberal immigration policy, despite the fact that Merah was a French-born Muslim.