A French teenager forced to go into hiding for criticising Islam was on Thursday at the heart of a ferocious secularism row after the justice minister claimed her comments breached "freedom of conscience”.

The row initially erupted after a 16-year old schoolgirl called Mila got into a heated exchange on social media that ended in her receiving a torrent of death threats and being taken out of school for her own safety.

An avid singer from Lyon, southeastern France, Mila had engaged in a live “chat” with followers of her Instagram account.

During the exchange, she rebuffed repeated advances by one online suitor, saying she was lesbian, prompting insults about her sexuality.

Then the attacks took a religious bent, with zealots online reportedly accusing Mila of insulting "our God Allah, the one and only" and hoping that she would "burn in hell."