(CNN) -- U.S. Secretary of State Hillary Clinton lashed out Monday at Syrian authorities for not protecting U.S. and French embassies in Damascus, adding she felt its president "has lost legitimacy" and wants to deflect attention from a crackdown on peaceful protesters.
Clinton insisted that Syria must meet its "international obligations immediately" to safeguard diplomats and property, hours after U.S. officials say that hundreds descended on its embassy for the third time in four days, scaling its walls and inflicting considerable damage.
Demonstrators also tried to break into the French Embassy in the same Middle Eastern nation Monday, said Romain Nadal, a spokesman for the French Foreign Ministry. Security officers at France's embassy were forced to fire three warning shots, the embassy said on its Twitter account.
These incidents mark the latest escalation between Syrian and Western authorities, many of which have criticized reported violent crackdowns against anti-government demonstrators.
While not calling for President Bashar al-Assad's ouster, Clinton offered strong language condemning his government and stressing that its leader is "not indispensable." She said his regime "will not succeed in deflecting attention" for the violence
"From our perspective, he has lost legitimacy," the secretary said. "He has failed to deliver on the promises he has made."
Earlier, State Department spokeswoman Victoria Nuland official accused state-run media in Syria of "inciting" what she called "thugs" to attack the U.S. Embassy in Damascus on Monday.
The day earlier, U.S. Ambassador to Syria Robert Ford wrote a note on the embassy's Facebook page slamming Damascus for letting "an anti-U.S. demonstration proceed freely while their security thugs beat down olive branch-carrying peaceful protesters elsewhere."
Ford also met that day with Syria's foreign minister -- a meeting the State Department said was pre-planned, but that Syria said came because the ambassador had been summoned. Nuland said that Foreign Minister Walid Moallem then "pledged to do a better job" to protect the embassy, the perimeter of which is protected by local security forces.
"So no sooner does he make that pledge when, today, we have thugs going over the walls," Nuland said Monday, shortly before Clinton said that the United States had reiterated its demand for Syria to protect its embassy.
About 300 people gathered at the embassy chancery building, and some of them came over its walls and even got on the roof, Nuland said. Once inside the compound, they used spray paint, tossed tomatoes and eggs, broke windows and knocked out security cameras.
No shots were fired, said Nuland. A senior State Department official said that U.S. Marine guards, who "never left the facility or engaged with demonstrators," eventually helped lock-down the facility and ensure all inside were safe.
Local guards, working with Syrian police, then swept the area to ensure that it was clear of demonstrators, the official said.
Another mob, meanwhile, went to the U.S. ambassador's residence two blocks away and also scaled walls there, said the spokeswoman. There, they broke windows, threw food and sprayed paint.
No one was hurt in either locale. Nuland said the United States "will obviously hold the Syrian government accountable for the damages."
She said that Syria's government "failed" in its mission to protect diplomatic sites, and claimed that state-run Syrian TV "appeared to be inciting" the mobs.
Nuland accused Damascus of "seeking to make distractions around our embassy" as it seeks to end months of dissent by its own citizens. The Syrian Observatory for Human Rights has said that around 1,400 civilians and 350 security and military forces have died since the unrest began.
France and the United States have been at odds with Syria since Thursday's visit of their respective ambassadors to Hama.
Syrian human rights activists say the Syrian military has been fighting to crush protests in that city led by people seeking governmental reform. A Syrian official last week insisted no military operation was under way in Hama, despite the reports.
The Syrian government later condemned the ambassadors for visiting the city without permission. Syria's foreign ministry insisted the visit violated the Vienna Convention, a 1961 accord that sets ground rules as to how diplomats can operate in other nations. U.S. officials said that Syria's failure to protect the embassy violates that same agreement.
Ford said in a statement that the pro-government protesters had caused "some damage" at the embassy, drawing a contrast to the tactics employed in Hama by those opposed to the al-Assad government.
"They resorted to violence, unlike the people in Hama, who have stayed peaceful. Go look at the Baath or police headquarters in Hama -- no damage that I saw," the ambassador said.
The French Foreign Ministry issued its own statement Sunday saying its embassy was also besieged by demonstrators and faulting Syrian authorities for failing to stop the destruction of vehicles, the burning of French flags and other damage.
CNN's Jill Dougherty, Arwa Damon and Elise Labott contributed to this report.