Robert Ford, US ambassador to Syria,  has been subjected to incidents of intimidation by pro-government groups [AFP]

The United States ambassador to Syria has left the country, with Washington blaming Syrian President Bashar al-Assad's government for what it called "credible threats against his personal safety".

Mark Toner, the US State department spokesman, said on Monday that Robert Ford, who has visited several hubs of anti-government protest during the seven months of protests against Assad's rule, had returned to Washington this weekend.

Toner said the US embassy would remain open in Damascus and that the threats were specifically directed towards Ford. He added that Ford's return to Damascus would depend on a US "assessment of Syrian regime-led incitement and the security situation on the ground".

Ford has come in for heavy criticism in Damascus by pro-government supporters who have accused him of helping incite violence in the country.

Within hours of the news of Ford's departure, Syria recalled its ambassador to Washington, an official television station reported.

"Syria's ambassador to the United States, Imad Mustapha, will leave Washington for Damascus to hold consultations with Syrian leaders," Al-Ikhbariya television reported.

A US official noted that Ford was not officially "withdrawn" from Syria, but rather was called back for consultations.

Victoria Nuland, the State department spokeswoman, said the department wanted to talk with Ford about the situation in Damascus, which she called "quite tense," and added that they also wanted to give him "a little bit of a break".

During months-long anti-government uprising, Ford has courted the opposition and denounced Assad on Facebook. As the government instituted a deadly crackdown on protests, Ford defied a travel ban on Western diplomats by going to hotspots and meeting anti-government demonstrators.

Last month pro-government demonstrators threw stones, concrete blocks and tomatoes at Ford and his aides, as well as attacked their cars with metal bars, during their visit with an opposition figure in Damascus.

Deadly crackdown

The latest diplomatic crisis between Damascus and Washington came as 16 people were reportedly killed in violence in Syria since Sunday, including eight civilians in the central city of Homs, according to the Syrian Observatory for Human Rights.

The official Syrian news agency said of the Homs violence that "terrorist groups" fired at a taxi carrying university students on Sunday night, killing a young woman. Security forces arrested several people and seized automatic weapons and automatic rifles and Molotov cocktails, it said.

A Youtube video shot by activists purportedly showed a young protester in Homs dying from a gunshot that hit him while he was dragging a body off a street in al-Khalidiya district. Authenticity of the footage could not be confirmed as most foreign media have been banned from Syria, making it difficult to verify events on the ground.

Syrian authorities say they are fighting "armed terrorist groups" in Homs who have killed civilians, security forces and prominent figures. They blame the unrest across the country on such groups, which they say have killed 1,100 troops and police. The United Nations says the crackdown has killed 3,000 people, including 187 children.

Source: Agencies