By NASSER ARRABYEE and ALAN COWELL
SANA, Yemen — Turmoil in the Arab world linked to a contentious video denigrating the Prophet Muhammad spread on Thursday to Yemen, where hundreds of protesters stormed the United States Embassy, two days after assailants killed the American ambassador in Libya and crowds tried to overrun the embassy compound in Cairo.
News reports also spoke of a separate protest in Tehran, where around 500 Iranians chanting “Death to America” tried to converge on the Swiss Embassy, which handles United States interests in the absence of formal diplomatic relations with Washington. Hundreds of police officers held the crowds back from the diplomatic compound, which Swiss officials had evacuated as a precaution, Agence France-Presse said.
For a third straight day, protesters scuffled with police in Cairo, news reports said, while in Iraq, a militant Shiite group, Asaib Ahl al-Haq, once known for its violent attacks on Americans and other Westerners, said the video “will put all American interests in danger.”
In Sana, witnesses said Yemeni security forces had tried to disperse a crowd at the fortified embassy compound in the east of Sana, the capital. But protesters broke through an outer perimeter protecting the embassy, clambering over a high wall and setting fire to a building.
They were forced to retreat after trying to plunder furniture and computers, the witnesses said.
Security forces guarding the embassy fired into the air as protesters set fire to two vehicles and burned tires. Protesters tore down and burned an American flag, replacing it with their own banner proclaiming the Islamic faith, witnesses said.
There were no immediate reports of American casualties or that the protesters had managed to breach the main diplomatic buildings within the compound. Yemeni officials said an unspecified number of protesters were wounded and some were arrested. Hours after the attack started, smoke still rose from the area.
By early afternoon, one witness, Yahya Yousef, who lives opposite the embassy, said: “Now almost everyone is out, and firing has ceased. We saw protesters getting out with some stuff from inside.”
The protests came hours after a Muslim cleric, Abdul Majid al- Zandani, urged followers to emulate the protests in Libya and Egypt, Sana residents said. Mr. Zandani, a onetime mentor to Osama bin Laden, was named a ”specially designated global terrorist” by the United States Treasury Department in 2004.
The crowd gathered a day after the embassy warned Americans in a posting on its Web site that “in the wake of recent events in Libya and Egypt, there is the possibility of protests in Yemen, and specifically in the vicinity of the U.S. Embassy, in the coming days.”
“The U.S. Embassy continues to recommend that U.S. citizens avoid large gatherings. Even demonstrations or events intended to be peaceful can turn confrontational and possibly escalate into violence. U.S. citizens in Yemen are urged to monitor local news reports and to plan their activities accordingly,” the Web posting said.
Mohammed Albasha, a spokesman for Yemen’s embassy in Washington, D.C., said the government strongly condemned the attack on the United States embassy in Sana, and he said that there were no reported casualties.