v the french school at the centre of last week's terrorist attack has received further threats, including a message that the killing of a rabbi and three children was "just the beginning".

Jean-Paul Amoyelle, head of the Ozar Hatorah network of Jewish schools in France, told newspaper Le Parisien that he feared further assaults after the shooting at its Toulouse school by self-confessed extremist Mohamed Merah.

President Nicolas Sarkozy has called for a crackdown on extremist websites. "From now on, any person who habitually consults websites that advocate terrorism or that call for hate and violence will be punished. France will not tolerate ideological indoctrination on its soil," he said.

But as most of France mourned the murders, more antisemitic incidents were recorded in the country.

In Toulouse, supporters of Merah have reportedly been gathering on the housing estate where he grew up, and copycat demonstrations have been held across the country.

A video of the killings, filmed on a camera around Merah's neck, has been sent to the Al-Jazeera TV station, but police said that the video had not been sent by the killer. The channel decided not to show the video, which is set to music and features subtitles with Koranic verses. Cries of the victims and gunshots can be heard on the original footage.

Pupils at a school in Rouen walked out of an English class after the teacher asked her students to observe a minute's silence for Merah, claiming that the killer was a "victim" whose links to al-Qaeda had been fabricated. Pupils who left the classroom wrote to the principal in disgust.

In Paris, a 12-year-old Jewish boy was assaulted outside his school, and bullet-holes were found in a window of the Yitzhak Rabin music school in the Sarcelles area of the city. In Dijon, a nightclub owner reported receiving death threats from an individual claiming to represent al-Qaeda and referring to the Merah shooting.

In the wake of the Toulouse tragedy, Brodetsky Jewish Primary School in Leeds is discouraging its pupils from wearing kippot while on trips, and will issue school uniform caps to avoid the children being identified as Jewish.

Headteacher Jeremy Dunford said the policy was in place to meet parental concerns, but it was "a hard line to walk … One thing we teach our pupils is that we are proud to be Jewish, and to hide that away is a sad situation to be in."