It is reported areas of Homs and the Houla region came under heavy shelling as Syrian troops tried to retake them from rebel forces.
The violence came as the Syrian Observatory for Human Rights said rebels captured Khirbat al-Joz in the province of Idlib, another step towards the Free Syrian Army establishing a stronghold across the country.
The British-based Observatory claims almost 80 percent of towns along the Turkish border are no longer under the control of Damascus.
But the intense fighting here has dramatically raised tensions with Syria’s former ally, which remains poised for a potential conflict after Syrian mortar bombs landed on its soil.
Turkish Prime Minister Tayyip Erdoğan dismissed assurances from Damascus that the attack was an accident saying Syrian fire had repeatedly hit Turkey. He warned Syria not to make the “fatal mistake” of testing Turkey’s resolve.