"Eleven prisoners were killed in the explosion which targeted a prison truck on the road between Idlib town and the village of Mastumeh," the Britain-based group's chairman, Rami Abdel Rahman, told AFP by telephone.
A number of security personnel accompanying the prisoners were wounded, Abdel Rahman said, without being able to provide details.
Separately, the Observatory reported that a member of the security forces was killed in fighting between dissidents and soldiers at Kfarnebel, in the Zawiya mountains of Idlib province, with troops using heavy machineguns.
It also said security forces had arrested seven people Saturday, including four members of the same family, in Iblin village.
The United Nations estimates that more than 5,400 people have been killed in Syria since anti-regime demonstrations erupted in March. (AFP)
