Syrian forces fired mortar bombs at a village in the northern province of Idlib on Tuesday, killing 10 people, nine of them from the same family, the Syrian Observatory for Human Rights said.
The Britain-based monitoring group said two of the dead were children. Many others were wounded, some of them critically, it added.
The shelling marks another violation of a shaky U.N.-brokered truce, which has already been marred by sporadic clashes and a string of explosions in the capital, Damascus, last week and central Idlib on Monday.
Violence appears to be rising again after a lull immediately after the ceasefire's implementation 19 days ago. Thirty United Nations monitors are already in Syria and the mission's number is expected to rise to 50 by the end of the week.