BEIRUT — Syrian government supporters smashed windows at the U.S. Embassy in Damascus on Monday, raised a Syrian flag and scrawled graffiti calling the American ambassador a “dog” in anger over the envoy’s visit last week to an opposition stronghold, witnesses said.

French Embassy security guards in the capital fired in the air to hold back supporters of President Bashar Assad’s regime who were also protesting the French ambassador’s visit to the same city, Hama, in central Syria. Protesters smashed embassy windows and shattered the windshield of a diplomatic SUV outside the compound. The French flag was removed and replaced with a Syrian one.

“God, Syria and Bashar. The nation that gave birth to Bashar Assad will not kneel,” read graffiti written outside the embassy. One witness said three protesters were injured when guards beat them with clubs. The witness asked not to be identified because of the sensitivity of the situation.

There was no immediate word on casualties among protesters at the American Embassy demonstration.

A U.S. official said the Obama administration will formally protest the attack and may seek compensation for damage caused when a mob breached the wall of the compound before being dispersed by Marine guards.

The official said the State Department would summon a senior Syrian diplomat on Monday to condemn the assault and demand that Syria uphold obligations to protect foreign diplomatic missions. The official said no buildings were entered and there were no injuries to embassy personnel. But the official said the attackers damaged the chancery building.

The official, who spoke on condition of anonymity because he was not authorized to discuss the matter publicly, said Syrian security forces were slow to respond to the attack.

The Syrian regime called the French and American ambassadors’ visits to Hama last week interference in the country’s internal affairs and accused the envoys of undermining Syria’s stability.

The protests erupted after U.S. Ambassador Robert Ford harshly criticized the Syrian government’s crackdown on a popular uprising.

Some 1,600 civilians and 350 members of security forces have been killed since demonstrations began, activists say. Syria blames what it calls “armed gangs” and Muslim extremists for the violence.

Hiam al-Hassan, a witness, said about 300 people had gathered outside the French Embassy while hundreds others were at the American diplomatic compound.

“Syrians demonstrated peacefully in front of the French embassy but they were faced with bullets,” said al-Hassan.

On Sunday, Ford attacked the Syrian government for allowing pro-government protests while beating up anti-regime demonstrators. The pro-Assad protests in Syria are known as “mnhebak,” or “we love you.”

“I have not seen the police assault a “mnhebak” demonstration yet,” Ford wrote on the embassy’s Facebook page. “On July 9, a “mnhebak” group threw rocks at our embassy, causing some damage. They resorted to violence, unlike the people in Hama, who have stayed peaceful.”

“And how ironic that the Syrian Government lets an anti-U.S. demonstration proceed freely while their security thugs beat down olive branch-carrying peaceful protesters elsewhere,” he said. “I saw no signs of armed gangs anywhere not at any of the civilian street barricades we passed,” Ford added.

Monday’s protests coincided with government-organized talks in Damascus on possible political reforms after four months of unrest.

However the talks did not stop Syrian forces from pressing their crackdown on the opposition.

Before the embassy attacks, Syrian troops stormed the country’s third-largest city with armored personnel carriers and heavy machine guns, a rights activist. At least two people were killed and 20 wounded in the attacks in Homs, activists said.

The clashes in Homs in central Syria suggest the Assad regime will not ease its four-month-old crackdown on the opposition despite proposing some political changes.

Vice President Farouk al-Sharaa called Sunday for a transition to democracy in a country ruled for four decades by the authoritarian Assad family dynasty. But the talks, which wrap up Monday, are boycotted by the main anti-government factions and are unlikely to produce any breakthroughs to immediately end the bloodshed.

The two days of meetings, however, were seen as a major concession by Assad’s regime after the most serious challenge to its rule.

In Homs, an activist in the city told The Associated Press clashes occurred after security forces on Sunday killed the son of an anti-regime tribal leader. The unrest lasted until 5 a.m. (0200 GMT) Monday.

Street lights were turned off then troops started entering neighborhoods, shooting with heavy machine guns atop Russian-made armored personnel carriers, said the activist, who spoke on condition of anonymity for fear of government reprisals.

He said some people cowered in their bathrooms during the height of the assault. At least one person was killed and 20 wounded, the activist said.

Rami Abdul-Rahman, the London-based director of the Syrian Observatory for Human Rights, also said forces pushed into parts of Homs.