A dawn bombardment by Syrian government forces have killed 10 civilians, a rights watchdog said, hours after UN chief Ban Ki-moon issued a new call for all sides to respect a troubled ceasefire.

Condemning bombings that killed mostly security force personnel, Ban said it was vital that government and opposition alike co-operate fully with the UN mission charged with overseeing a tenuous ceasefire that went into force on April 12.

Nine members of a single family were among the 10 dead in Idlib province in the northwest, the Britain-based Syrian Observatory for Human Rights said.

A mortar round slammed into their home in Mashmashan village near the town of Jisr al-Shughur, the watchdog said, adding that four women and two children were among the family members killed.