The protesters breached the usually tight security around the embassy and reached the compound grounds but did not enter the main building housing the offices.
Once inside the compound, they brought down the US flag, burned it and replaced it with a black banner bearing Islam’s declaration of faith – “There is no God but Allah.”
Demonstrators also removed the embassy’s sign on the outer wall, set tyres ablaze and pelted the compound with stones.
It was similar to an attack on the US embassy in the Egyptian capital of Cairo on Tuesday night and the mob attack on the US consulate in Libya’s eastern city of Benghazi, in which American Ambassador Chris Stevens and three other Americans died.
In Egypt yesterday, protesters were clashing with police near the US embassy in Cairo for the third day in a row.
The violence has raised worries further protests could break out around the Muslim world as anger spreads over the film.
Yemeni security forces who rushed to the scene in Sanaa fired in the air and used tear gas to disperse the demonstrators and were eventually able to drive them out of the compound. It was not immediately clear whether anyone was inside the embassy at the time of the attack.
The Yemeni embassy in Washington condemned the attack and vowed to ensure the safety of foreign diplomats and to step up security measures around their missions in the country.
Yemen is home to al Qaida’s most active branch and the US is the main foreign supporter of the Yemeni government’s counterterrorism campaign.
The government on Tuesday announced that al Qaida’s second most important leader in Yemen was killed in an apparent US airstrike, a major blow to the terror network.
The film Innocence of Muslims came to attention in Egypt after its trailer was dubbed into Arabic and posted on YouTube.
The trailer depicts Mohammed as a fraud, a womaniser and a madman in an overtly ridiculing way, showing him having sex and calling for massacres.
Although the video-sharing website blocked access to it on Wednesday, Egyptian protesters clashed yesterday with police near the US embassy in Cairo for the third day in a row. Police used tear gas to disperse the protesters and the two sides pelted each other with stones.
In Cairo, the Interior Ministry said 16 protesters and 13 policemen were wounded in the clashes. Twelve protesters have been arrested.
In Iraq, hundreds of Shiite followers of the anti-American cleric Muqtada al-Sadr demanded the closure of the US embassy in Baghdad. Protesters burned American flags and carried banners reading, “We reject the attack on the Prophet Mohammed.
“No, no, to Israel! No, no to America!” thousands shouted in the Shiite stronghold of Sadr City in northeast Baghdad. “Yes, yes for Messenger of God.”
The protests in Yemen and Egypt point to an increased boldness among Islamists who have become more powerful amid the turmoil since last year’s revolts deposed authoritarian regimes.
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 with machine guns and rocket-propelled grenades overwhelmed the American Consulate in Benghazi late on Tuesday, killing the ambassador and three other Americans and ransacking the building. US officials suspect the assault may have been a planned operation rather than a spontaneous mob assault.