SANAA, Yemen (AP) — Chanting “death to America,” hundreds of protesters angered by an anti-Islam film stormed the U.S. Embassycompound 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.

American missions have been attacked this week in three Arab nations — Yemen, Egypt and Libya — that have faced persistent unrest and are struggling to restore law and order after last year’s revolts deposed their authoritarian regimes.

The protests in Yemen and Egypt point to an increased boldness among Islamists who have become more powerful amid the turmoil since the revolts. 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 Islamists feel they can act with impunity.

The violence this week in Libya was of a different degree altogether. While protesters in other countries were unarmed, a crowd bristling with machine guns and rocket-propelled grenades overwhelmed the American Consulate in Benghazi late Tuesday, killing the ambassador and three other Americans and ransacking the building. U.S. officials suspect the assault may have been a planned operation rather than a spontaneous mob assault.

In the Yemeni capital on Thursday, protesters smashed windows as they breached the embassy perimeter and reached the compound grounds, although they did not enter the main building housing the offices.

Angry young men brought down the U.S. flag in the courtyard, burned it and replaced it with a black banner bearing Islam’s declaration of faith — “There is no God but Allah.”

Afghanistan’s government, meanwhile, sought to avert any protests as past anger over perceived insults to Islam has triggered violence in the country.

President Hamid Karzai canceled an official visit to Norway and spoke by phone with U.S. President Barack Obama to convey his condolences for the deaths of the U.S. ambassador to Libya and three other diplomats, a statement said. He also discussed the “film and the insulting of holy Islamic values,” but the statement provided no other details.

Stevens was the first U.S. ambassador killed in the line of duty in 30 years.

The movie, “Innocence of Muslims,” came to attention in Egypt after its trailer was dubbed into Arabic and posted on YouTube. The video-sharing website blocked access to it Wednesday. The trailer depicts Muhammad as a fraud, a womanizer and a madman in an overtly ridiculing way, showing him having sex and calling for massacres.

h/t: Yahoo! News