Security guards at the French embassy in Syria have used live ammunition to prevent hundreds of government loyalists from storming the building.
A French foreign ministry official said the Syrian authorities had done nothing to stop the assault on its embassy in the capital, Damascus.
Pro-government demonstrators also broke into the US embassy. An official in Damascus told the BBC that the offices had come under attack by a "mob".
The official said the Syrian government had given assurances they would provide adequate protection for the embassy but that on this occasion, the authorities were slow to respond.
Officials told Reuters attackers tore down US embassy plaques and tried to break security glass.
A US State Department spokesperson said the assault had been encouraged by a pro-government television station.
The protests followed visits by US and French ambassadors to the city of Hama, the focus of demonstrations against Persident Bashar al-Assad's rule.
The Syrian government sharply criticised the visits which the US and France had said were meant to express solidarity with the anti-government protesters.
France has led Western attempts to pass a United Nations Security Council resolution condemning Syria's hierarchy for cracking down on protesters.
It says the president has lost legitimacy because of the number of killings to try to quell the protests demanding political freedoms after 41 years of Assad family rule.