An explosion killed at least 11 people on a minibus carrying prisoners in Syria's northwestern province of Idlib on Saturday, the opposition Syrian Observatory for Human Rights reported.
The British-based group, which monitors a 10-month-old uprising against Syrian President Bashar al-Assad, gave no further details. No independent confirmation was available.
In other violence, heavy fighting broke out between the Syrian army and soldiers who have defected to join anti-Assad insurgents in an area near the border with Turkey, Al Jazeera television reported.
It gave no further details of the clashes which it said were in the city of Jisr Al Shughour.