Three people have been injured after crowds loyal to Syrian President Bashar al-Assad attacked the US and French embassies in Damascus.

The foreign ministry in Paris said three French staff were wounded in the attack on its embassy. There were no injuries reported at the US embassy.

Guards at the French embassy fired three warning shots during the incident.

As Syrian security forces looked on, Assad supporters smashed their way into the compound with a battering ram, broke windows and destroyed the ambassador's car, according to a spokesman in Paris.

An AFP photographer at the scene said several windows in the French embassy were broken and Syrian flags were raised.

The US embassy official told AFP: 'Today there was an attack by a mob on the US embassy,' adding the crowd caused some damage to the mission.

The US embassy official said 'no staff were injured' and were never in 'imminent danger,' although the 'Syrian government was slow to respond with extra security measures that were needed.'

Monday's embassy attacks come four days after US Ambassador Robert Ford and his French counterpart Eric Chevallier visited the central city of Hama, 21km north of Damascus, sparking outrage in the capital.

Separately, Syrian forces killed at least one civilian and injured 20 in Homs during the heaviest raids on the city since troops deployed there two months ago to crush dissent against Assad.