Protesters Storm US Embassy in Yemen in New Attack Chanting "death to America" and "death to Israel," hundreds of protesters angered by an anti-Islam film stormed the U.S. Embassy compound in Yemen's capital and burned the American flag on Thursday, the latest in a series of attacks on American diplomatic missions in the Middle East. The string of assaults this week, in Yemen, Egypt and the storming of a U.S. consulate in Libya that killed four Americans, point to an increased boldness among Islamists who have become more powerful since last year's wave of revolts toppled authoritarian leaders. The anger over the movie denigrating Islam's Prophet Muhammad has also put the region's new leaders - some of whom are themselves Islamists - in a difficult corner, between a base demanding a free hand to respond to the insult and U.S. pressure to crack down. In the past, protests have broken out over perceived insults to Islam from the West, but in Arab countries they never escalated to the degree of breaching embassies, suggesting now hard-liners feel they can act with impunity. Yemen's president, Abed Rabbo Mansour Hadi, quickly apologized to the U.S. for the embassy attack and vowed track down the culprits, just as Libya's president did. Egypt's Islamist President Mohammad Morsi, who had been slow to speak out on Tuesday's assault on the embassy in Cairo, promised Thursday that his government would not allow attacks on diplomatic missions. Yemeni protestors break windows of the U.S. Embassy during a protest about a film ridiculing Islam's Prophet Muhammad, in Sanaa, Yemen, Thursday, Sept. Dozens of protesters gather in front of the US Embassy in Sanaa to protest against the American film "The Innocence of Muslims" deemed blasphemous and Islamophobic. (AP Photo/Hani Mohammed) Close U.S. officials suspect the Libya assault may have been a planned terror operation rather than a spontaneous mob assault. While protesters in other countries were unarmed, a crowd bristling with machine guns and rocket-propelled grenades overwhelmed the consulate in Benghazi late Tuesday, killing the ambassador and three other Americans. Protests are also erupting in other countries. In Egypt, protesters clashed with riot police who had pushed them away from the embassy the night before. In Iraq, several hundred Shiite hardliners protested in Baghdad's Shiite stronghold of Sadr City. The leader of an Iranian-backed Shiite militia that previously attacked U.S. troops, Asaib Ahl al-Haq, threatened anti-U.S. attacks. The movie "will put all the American interests in Iraq in danger," the militia leader, Qais al-Khazali, told The Associated Press. In Iran, about 50 protesters shouted, "Death to America," outside the Swiss Embassy, which looks after U.S. diplomatic interests in Iran. Riot police kept the crowd away from the building. Hundreds converged Thursday on the U.S. Embassy in the Yemeni capital Sanaa, which is heavily barricaded because of past al-Qaida-linked attacks on the compound. Yemeni guards at checkpoints on roads leading up to the compound did nothing to stop the crowd, said Ahmed Darwish, a witness who was at the scene. The crowd swarmed over embassy's entrance gate. Men with iron bars smashed the thick, bullet-proof glass windows of the entrance building while others clambered up the wall. Some ripped the embassy's sign off the outer wall. Inside the compound grounds, they brought down the American flag in the courtyard and replaced it with a black banner bearing Islam's declaration of faith - "There is no God but Allah." They did not enter the main building housing the embassy's offices, some distance away from the entry reception. Demonstrators set tires ablaze and pelted the compound with rocks.