A "mob" attacked the U.S. Embassy in Syria on Monday, an official who was inside the embassy told CNN.
Several demonstrators climbed over a fence at the compound in Damascus, a senior U.S. State Department official said.
The building was not breached and protesters were later dispersed by the Syrian government, the official said.
Demonstrators also tried to break into the French Embassy, said Romain Nadal, a spokesman for the French Foreign Ministry. Nadal said the protest had ended, but gave no further details.
The official who was inside the U.S. Embassy said the the building sustained some damage but no personnel were injured.
"Today the U.S. Embassy was attacked by a mob" throwing rocks and using other destructive measures, the official said, adding that the attack lasted a few hours.
The Syrian government was slow in responding with additional security measures, the embassy official said. "We call on the Syrian government to abide by the protections required under the Vienna convention."
"This is an unfortunate distraction because the Syrian government continues to beat, imprison, torture and kill people who want to peacefully protest," the embassy official said.
In recent days, both the U.S. and French embassies have seen demonstrations by angry Syrians supporting the regime of President Bashar al-Assad.
The U.S. and French ambassadors last week visited Hama, a city in which the Syrian military has been fighting to crush protests by people seeking governmental reform, according to Syrian human rights activists. A Syrian official insisted no military operation was under way in Hama.
On Sunday, U.S. Ambassador to Syria Robert Ford slammed the Syrian government for letting "an anti-U.S. demonstration proceed freely while their security thugs beat down olive branch-carrying peaceful protesters elsewhere."
In a note on the embassy's Facebook page, Ford also said the United States respects "the right of all Syrians - and people in all countries - to express their opinions freely and in a climate of mutual respect. We wish the Syrian government would do the same."
On Saturday, protesters supporting al-Assad's government "threw rocks at our embassy, causing some damage," Ford said in the statement. "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."
Opponents of Assad's regime, calling for governmental reform in Syria, have been met with violence in Hama and elsewhere, human rights activists and witnesses have told CNN.
CNN's Arwa Damon and Elise Labott contributed to this report.