The offices of the French satirical magazine Charlie Hebdo have been burned out in a petrol-bomb attack, the day it was due to publish an issue with a cover appearing to make fun of Islamic law.

The magazine had revealed that it was publishing “Charia Hebdo” and named the Prophet Mohammed “editor-in-chief” for the issue, which hit the news stands today.

The magazine’s editor, known only as Charb, told France Inter radio that for the past few days the paper had received threats on Twitter and Facebook and by post, which had been passed on to police. He said he was sickened and angry that “violence could be used to counter drawings”.