Israeli attacks on Gaza have let loose an unprecedented wave of hate on media websites and social networks in France that moderators say they are struggling to contain.

According to The Local the bombardment of Gaza has enflamed tensions particularly in France, which has Western Europe’s largest Muslim population as well as largest Jewish population.

Street protests in Paris in support of Gaza have ended with attacks on two synagogues and violence directed against police, who responded with tear gas.

Now David Corchia, head of Concileo, a firm of moderators that has the newspapers Le Figaro and Libération as clients, told AFP: “As soon as you talk about Israel, it crystallises all passions, with up to 20,000 or 30,000 comments sometimes after an article, of which we will only let five to 10 per cent through.”

French law bans racist, anti-Semitic or discriminatory messages, as well calls for violence. Computer software helps moderators filter comments by spotting suspect key words. The rejection rate can reach 95 per cent on the topic of the Israeli-Palestinian conflict.

Another moderator for news websites said: “There are three times as many comments than normal, all linked to the Israeli-Palestinian conflict. We see racist or anti-Semitic messages, very violent, that also take aim at politicians and the media, sometimes by giving journalists’ contact details. This sickening content is peculiar to this conflict. The war in Syria does not trigger these kinds of comments.”

Comments about the conflict can be found on any subject. “On an article about the Tour de France, after four comments it’s about Gaza. On one story about salmon fishing, I saw a comment saying: ‘Stop talking about this, the problem is there are too many Jews.'”

Pierre Duhau-Laurent, marketing director for Atchik Services, which moderates the websites of the French presidency and the Le Parisien daily, said “organised propaganda” was currently sweeping social networks at night.

“Calls for murder are our daily life. It’s sometimes hard psychologically for our moderators.”