The Syrian Observatory for Human Rights says an assault by tanks and naval vessels on the port city of Latakia to crush demonstrations against President Bashar al-Assad, has killed at least 21 civilians.
The organisation says most of the casualties, including tens of wounded, were from big calibre machineguns fired from tanks on southern quarters of the city, which were also hit by Navy vessels.
The BBC reports the operation began on Saturday with armoured vehicles and troops moving in.
Some 20 tanks and personnel carriers were said to be taking part in the Latakia assault along with at least two gunboats.
Latakia has seen many anti-government protests in the past six months.
More than 1700 people have reportedly died in the uprising against the rule of President al-Assad.