(VOVworld) - France's biggest satirical weekly, "Le Canard Enchaine" said it received an email with a gruesome death threat the day after Islamist gunmen shot dead 12 people at the office of Charlie Hebdo magazine. Surveillance was strengthened and police have started an investigation.

In another development, Charlie Hebdo depicted the Prophet Muhammad on its first cover since the attack. The latest cover shows a weeping Muhammad, holding a sign reading "I am Charlie" with the words "All is forgiven" above him to express solidarity with France. An Egyptian Muslim organization Dar al-Ifta said the front page has provoked 1.5 billion Muslims and is likely to result in a new wave of hostility in France. Meanwhile, Muslim groups in France urged the Muslim community to stay calm and avoid extreme reactions.

On the same day, at a ceremony to commemorate 3 police officers who were killed in the Charlie Hebdo attack, French President Francois Hollande said France will never surrender to any threats from extreme Muslims.