Muslims angered by cartoons mocking the Prophet Mohammad should follow his example of enduring insults without retaliating, Egypt’s highest Islamic legal official said on Thursday.Western embassies tightened security in Sanaa, fearing the cartoons published in a French magazine on Wednesday could lead to more unrest in the Yemeni capital where crowds attacked the U.S. mission last week 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 Shi’ite Muslims demonstrated in the northern Nigerian town of Zaria, burning an effigy of U.S. 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 on Friday against the cartoons. Four people died and almost 30 others were wounded last week when protesters incensed by the movie about Prophet Mohammad stormed the U.S. 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 U.S.-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.