Protesters angered by an anti-Islam film made in the US have stormed the grounds of the American embassy in the Yemeni capital, Sanaa.
Police opened fire in an attempt to hold back the crowds, but failed to prevent them gaining access to the compound and setting fire to vehicles.
A number of people were reported to have been injured.
On Tuesday, the US ambassador to Libya was killed in a fire started after the US consulate in Benghazi was stormed.
Earlier on Thursday, US officials said they were investigating whether the attack in Libya – which killed three other US consul staff and several Libyans – was planned, citing suspicions that a militant jihadist group may have co-ordinated the violence.
There have also been clashes in the Egyptian capital, Cairo.
On Wednesday, demonstrators in Cairo angry at the film – Innocence of Muslims – breached the walls of the US embassy and tore down the flag. Clashes continued in the early hours of Thursday morning.
President Mohammed Morsi has appealed for calm, saying Egyptians “reject any kind of assault or insult” against the Prophet Muhammad.
“I condemn and oppose all who… insult our prophet. [But] it is our duty to protect our guests and visitors from abroad,” he said in a statement broadcast by state media.
“I call on everyone to take that into consideration, to not violate Egyptian law… to not assault embassies.”
BBC
