Security forces were gathering in Khan Sheikhun and Maarat al-Numan, a town of 90,000 between Damascus and Aleppo.

UN Secretary General Ban Ki-moon has urged Syria to halt the bloodshed and "stop killing people".

The UN says that at least 1,100 people have died as the government has violently sought to quash protests over the past three months.

State television said late on Thursday that President Bashar al-Assad's cousin, Rami Makhlouf, intends to give up his business interests - which span telecommunications, construction and oil - and donate his profits to charity.

Mr Makhlouf is one of a number of Syrian officials on the European Union's sanctions list, which includes asset freezes and travel bans.

President Assad is facing the gravest threat to his family's 40-year ruling dynasty, as unrest that first erupted in the south of the country has now engulfed the north - near the border with Turkey - and is threatening to spread eastwards towards its border with Iraq.