CAIRO - Egyptians angry at a film they said was blasphemous to Islam on Friday hurled stones at a line of police in Cairo blocking the route to the U.S. embassy, where demonstrators climbed the walls and tore down the American flag earlier this week. "God is greatest" and "There is no god but God", one group near the front of the clashes chanted, as police in riot gear fired tear gas and threw stones back in a street leading from Tahrir Square to the embassy nearby. About 300 people had gathered to protest, some waving flags with religious slogans. State media reported that 224 people had been injured since Wednesday night. The initial protest, in which the embassy walls were scaled, took place on Tuesday. The Muslim Brotherhood, the group that propelled President Mohamed Mursi to power, had called for a peaceful nationwide protest against the film on Friday after it sparked demonstrations across the region. Many Muslims regard any depiction of the Prophet Mohammad as blasphemous. The US ambassador in Libya was killed by gunmen on Tuesday and the US mission in Yemen was attacked by protesters on Thursday. Mursi, Egypt's first freely elected president, has to strike a delicate balance, fulfilling a pledge to protect the embassy of a major aid donor while also being seen by his Islamist backers to take a strong line against the film. Mursi said on Thursday he had spoken to U.S. President Barack Obama and had asked him to act against those seeking to harm relations. His Cabinet said Washington was not to blame for the film but urged legal action against those insulting religion. "Before the police, we were attacked by Obama, and his government, and the Coptic Christians living abroad," shouted one protester, wearing a traditional robe and long beard favoured by some ultra-orthodox Muslims, as he pointed to the police cordon.