The Syrian army has intensified its offensive on Sunni strongholds and opposition forces are fighting fire with fire.
Amateur footage posted online shows violent clashes in and around the central city of Homs, with activists reporting aerial bombing and artillery fire.
They also say that 15,000 Sunni civilians are trapped in the outskirts, after President Bashar al-Assad’s forces attempted to close off the city.
Another video uploaded to the Internet purports to show Syrian army tanks being blown up on the streets of Daraya, south west of the capital Damascus.
Thousands of people are fleeing the battle-torn country every day.
The United Nations says the number of Syrian refugees registered in neighbouring countries is nearly 700,000, with the actual number much higher.
The UN has commended Turkey, Jordan and Lebanon for keeing their borders open and urged them to continue.