Activists and witnesses in Syria say troops in tanks stormed into the central city of Hama early Sunday, killing at least 13 people.

The witnesses say there has been heavy gunfire in Hama, which has been the scene of large protests against President Bashar al-Assad.

Activists say Mr. Assad is trying to crush the largely peaceful uprisings that broke out across much of the country in March, protesting his 11-year rule.

Rights groups say Syrian forces have killed at least 1,600 civilians during the government's crackdown on dissent. The government has blamed much of the violence on terrorists and militants who it says have killed hundreds of security personnel.

It is hard to verify accounts of the unrest in Syria because the government has barred most foreign media from reporting and traveling freely in the country.

France recently condemned Syria for what it called “repression” and the continued arrests and killings of civilians.

The Foreign Ministry then issued a statement that Syria prohibited French and U.S. envoys from traveling outside of Damascus without permission.

The two ambassadors angered Syrian officials earlier this month when they traveled to Homs to show solidarity with residents in a city hit with violence.