CAIRO — Egypt's president said on Thursday he supported peaceful protest but not attacks on embassies, after Egyptians angry at a film deemed insulting to the Prophet Mohammad climbed into the U.S. embassy in Cairo and tore down the American flag.

"Expressing opinion, freedom to protest and announcing positions is guaranteed but without assaulting private or public property, diplomatic missions or embassies," Mohammed Morsi, an Islamist who is Egypt's first freely elected president, said.

He pledged to protect foreigners in Egypt.

The incident will test Morsi's handling of ties with the United States, a close ally of Egypt under ousted President Hosni Mubarak and which has long been wary of Islamists. Washington is a major aid donor to Cairo. Mubarak was toppled in a wave of popular protests.

Morsi needs to strike a balance by addressing the anger of many Muslims at the film that portrayed the Prophet as a philanderer and religious fake, enraging Muslims across the Middle East. Many Muslims believe depicting the Prophet in any form is blasphemous.

The U.S. ambassador to Libya and three other staff were killed when the U.S. consulate in Benghazi was attacked overnight on Tuesday.

Protesters on Thursday also stormed the U.S. embassy in Yemen.

Police and demonstrators were scuffling on Thursday near the U.S. embassy in central Cairo as Morsi's recorded address was televised. Young men hurled stones at a police cordon blocking the road leading to the embassy. Police fired teargas.

The state news agency said 13 people were injured in the violence that erupted on Wednesday night.

"All of us Egyptians reject any form of attack or insult to the Prophet," Morsi said, while also offering his condolences over the killing of the U.S. ambassador and diplomats in Libya.

Morsi said he had spoken to U.S. President Barack Obama on Thursday. "I affirmed to him the need for deterrent legal measures against those who want to damage relations between peoples, and particularly between the people of Egypt and the people of America," he said.

At least one of the promoters of the film "Innocence of Muslims" is an Egyptian Coptic Christian who lives in the United States. Clips of the film have circulated on the Internet for weeks, stoking anger among Muslims.

Morsi later told a news conference in Brussels he would protect foreigners and diplomatic missions in Egypt. He was in Brussels for his first visit to Europe since becoming president in June