Writer Ghislain Gilberti and his son were savagely attacked on Saturday by a group of men shouting “filthy white”, seemingly Islamists enraged by one of his novels, police in France have heard.

Mr Gilbert and his 12-year-old son were attacked in Belfort, France on Saturday following harassment and attempted break-ins. Though an active antifascist, the writer and his family have received death threats from Salafists displeased that the prologue title of the novelist’s bestseller is “jihad”.

Police are investigating after Mr Gilberti was taken to hospital with a broken arm by firemen, following a reported street attack by Salafist Muslims.

Mr Gilberti said he received blows to his back before being called a “filthy white” by four men aged between 20 and 30 years, who held him down while attacking.

The author reported the men also kicked his 12-year-old son in the head and stomach, shouting “it’s the same price for you” and “we don’t forgive, we don’t forget” at his 11-year-old daughter who was also present.

The thriller novelist lost consciousness during the beating and, following the attack, will again request full police protection, Mr Gilberti’s publisher broadcast on Facebook.

Police say they are aware of the incident, have interviewed witnesses and that they are currently trying to determine the circumstances of the assault.

L’est Republicain reported that Salafists began threatening the author and his family, and harassing them in their own home following the paperback release of Mr Gilberti’s novel The Feast of the Snake.

The book features a fictional jihadist group who finance their actions by means of international drug trafficking. The novelist was assigned temporary police protection following incidents in March.

Mr Gilberti said he suspects Muslim critics who denounce his novel as “insulting [their] cause” are unintelligent. He remarked: “The authors of the threats have not read the book, or they have just skim read it. I did not insult Islam in the book. I am rather a defender of all faiths and I combat racist acts in an anti-fascist movement.”