By Edmund Blair
CAIRO (Reuters) - 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 U.S. ambassador in Libya was killed by gunmen on Tuesday and the U.S. 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 favored by some ultra-orthodox Muslims, as he pointed to the police cordon.
Egypt's Coptic Orthodox church has condemned what it said were Copts abroad who had financed the film.
"NO LONGER AN ALLY"
In the middle of the street lay an overturned and burnt out car. Behind the police line, the authorities had erected a wall of large concrete blocks barring access to the fortress-like embassy, which is close to Tahrir, the center of protests against ousted former President Hosni Mubarak and the scene of many demonstrations since.
The United States, a close ally of Egypt under Mubarak, has long been wary of Islamists, only formally opening contacts with the Muslim Brotherhood last year, several months after Mubarak's 30-year rule was ended by a popular uprising.
Al-Masry Al-Youm highlighted comments Obama made to a Spanish-language network saying Egypt was neither an enemy nor an ally. "America: Egypt is no longer an ally," the daily newspaper wrote in a front page headline.
The United States has a large embassy in Cairo, partly because of a vast aid program that began after Egypt signed a peace deal with Israel in 1979. Washington gives $1.3 billion in aid each year to the army plus additional funds to Egypt.
Though some demonstrators wore clothes favored by ultra-orthodox Islamists, many were young men in jeans and T-shirts. Some perched on barriers along the street watching the ebb-and-flow, as demonstrators pushed forward to hurl stones, and then ran back towards Tahrir under a volley of tear gas.
"I came here to have a look at the people, to see what they are saying and see if what they say is right," said Mohamed Ahmed, sitting with friends as teargas wafted through the air.
Some Egyptians have been angered by the violence. One picture circulating on Facebook showed a burnt out car accompanied by the words: "People go to defend the Prophet with petrol bombs and religious insults to the police. They don't pray at noon or in the afternoon. Who are they?"
Police had tried to clear the street leading to the embassy and Tahrir around dawn on Friday with clouds of teargas after a second night of violence. But protesters returned soon afterwards.
One banner held aloft by demonstrators read: "It is the duty of all Muslims and Christians to kill Morris Sadek and Sam Bacile and everyone who participated in the film."
The two people named are both linked to the film. Sadek, a Copt living in the United States, told Reuters this week he promoted the film to highlight discrimination against Christians who make up about 10 percent of Egypt's 83 million people.
(Additional reporting by Marwa Awad; Editing by Andrew Osborn)