At least five people have been killed in Syria after security forces opened fire on anti-government protesters, as the Syrian government continues its crackdown on dissent.

Activists said Friday that protesters were killed in several areas, including the central cities of Homs and Hama.

Thousands of demonstrators took to streets across the country after midday prayers, renewing calls for President Bashar al-Assad's departure.

Some demonstrators rallied in support of army deserters in the central town of Rastan, who are engaged in a third day of fighting against government forces.

Earlier Friday, Syrian officials said seven soldiers and police personnel were killed in an operation targeting what they called “terrorists” in Homs province.

The state news agency says the deaths took place amid the offensive in Rastan. Syrian troops have been trying to crush the army deserters who have formed rebel units around the town.

Meanwhile, U.S. Secretary of State Hillary Clinton called on Syrian authorities to protect foreign diplomats after a pro-government mob attempted to assault U.S. Ambassador Robert Ford and other American diplomats as they arrived for a meeting with a leading opposition figure in the capital, Damascus.

Ford was confronted by an angry mob as he prepared to meet Hassan Abdel-Azim, a moderate who has demanded an end to Mr. Assad's crackdown on dissent as a condition for any opposition dialogue with the government.

Clinton called Thursday's incident “wholly unjustified” and demanded that Syrian authorities fulfill their international obligations to protect all foreign diplomats and diplomatic property.

On Friday, U.S. State Department spokeswoman Victoria Nuland said it was “incomprehensible” and “unacceptable” that it took Syrian forces almost two hours to come to Ford's assistance.