At least six people were killed in Syria on Friday where security officers have responded to mass protests with force.

The deaths occurred after tens of thousands of anti-government demonstrators rallied for President Bashar al-Assad's resignation, in what has become the most serious challenge yet to his 11-year rule.

Witnesses and activists say the deaths occurred in areas including the Damascus suburbs, northwestern Idlib province and the flashpoint city of Homs.

The reports say at least five other people were killed in Homs overnight, after the military launched a massive crackdown in the city.

On Thursday, residents and activists said tanks moved into Homs to block off neighborhoods as government forces conducted raids and made arrests.

Meanwhile, activists say security forces used batons and tear gas to push back demonstrators in mostly Kurdish Hasaka province region on Friday.

There are reports of demonstrations in other cities, including Dara'a and Latakia.

Also, state-run news reports say supporters of Mr. Assad have unfurled Syrian flags and rallied in several cities.

In a separate development, France condemned Syria for what it called “repression” and the continued arrests and killings of civilians.

The Foreign Ministry issued a statement on Friday after Syria prohibited French and U.S. envoys from traveling outside of Damacus without permission.

The two ambassadors angered Syrian officials earlier this month when they traveled to Homs to show solidarity with residents.

Last Friday, at least 32 people were killed after Syrian security forces opened fire on tens of thousands of demonstrators during some of the largest protests to date against Mr. Assad's government.

It is difficult to verify accounts of the violence in Syria because its government has barred foreign media from reporting and traveling freely in the country.