France has increased security at its embassies and consulates across the world following the publication of cartoons depicting the Muslim Prophet Muhammad in a French magazine.
French embassies and schools in 20 countries will be closed over the next few days.
The cartoons were published in satirical magazine Charlie Hebdo, which had its offices set on fire after publishing similar caricatures last year.
Riot police have also been deployed around the Paris offices of the weekly publication amid fears of another attack.
Egypt's highest Islamic legal official said today that Muslims angered by the cartoons should follow his example of enduring insults without retaliating.
Condemning the publication of the cartoons as an act verging on incitement, Grand Mufti Ali Gomaa said it showed how polarised the West and the Muslim world had become.
Mr Gomaa said Muhammad and his companions had endured "the worst insults from the non-believers of his time. Not only was his message routinely rejected, but he was often chased out of town, cursed and physically assaulted on numerous occasions.
"But his example was always to endure all personal insults and attacks without retaliation of any sort. There is no doubt that, since the Prophet is our greatest example in this life, this should also be the reaction of all Muslims."
His statement echoed one by Al Azhar, Egypt's prestigious seat of Sunni learning, which condemned the caricatures showing the Prophet naked but said any protest should be peaceful.
An official at the Coptic Orthodox Church in Egypt also condemned the cartoons as insults to Islam.
Last week some Egyptian protesters scaled the US Embassy walls and tore down the flag.
They clashed with police for four days, although most of the thousands of Egyptians who took to the streets did so peacefully.
In the Yemeni capital Sanaa, western embassies tightened security today, fearing the cartoons could lead to more unrest.
Last week crowds attacked the US mission there over an anti-Islam film made in America.
In the latest of a wave of protests against that video in the Islamic world, several thousand Shia Muslims demonstrated in the northern Nigerian town of Zaria, burning an effigy of US President Barack Obama and crying "Death to America".
The cartoons in France's Charlie Hebdo satirical weekly have provoked relatively little street anger so far, although about 100 Iranians demonstrated outside the French embassy in Tehran.
In Tunisia, the birthplace of the Arab Spring revolts, the Islamist-led government decreed a ban on protests planned tomorrow against the cartoons.
Four people died and almost 30 others were wounded last week when protesters incensed by the movie about Prophet Muhammad stormed the US embassy.
An Islamist activist called for attacks in France to avenge the perceived insult to Islam by the "slaves of the cross".
Mu'awiyya al-Qahtani said on a website used by Islamist militants and monitored by the US-based SITE intelligence group: "Is there someone who will roll up his sleeves and bring back to us the glory of the hero Mohammed Merah?"
He was referring to an al-Qaeda-inspired gunman who killed seven people, including three Jewish children, in the southern French city of Toulouse in March.
