Syrian activists say soldiers backed by tanks have fired on citizens during a raid in the flashpoint city of Hama, killing at least 80 people.

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. Some estimates say as many as 140 have died in the violence.

Activists at the scene say the sound of machine guns and tank shells echoed across Hama Sunday. Medical officials say hospitals are overrun with wounded people and are in desperate need of blood donations.

Witnesses say troops started their attack at dawn, firing randomly and breaking down roadblocks erected by civilians to keep troops out of the city.

Citizens have held large protests against President Bashar al-Assad in Hama, an important city in the history of Syrian resistance. In 1982, the current president's father, President Hafez al-Assad, used military force to quell a rebellion there, killing thousands of people.

In the country's south early Sunday, residents say security forces killed three people and wounded several others as they stormed the village of al-Hirak. They say forces also arrested more than 100 people in the raid.

Activists say President Assad is trying to crush the largely peaceful uprisings against his government that broke out across much of the country in March.

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.