The ceasefire has been violated repeatedly in the past two years, with dozens of people killed and injured.
The British-based Syrian Observatory for Human Rights, an opposition war monitor, reported that government forces fired about 30 rockets into rebel-held areas, including the Maram camp on Sunday morning, killing six and wounding 25. female.
The tent settlement is located just northwest of the provincial capital of Idlib.
Rebel groups responded by shelling government positions with artillery and rockets in the Saraqib area, east of Idlib, and the al-Ghab plain, the observatory reported.
The opposition Syrian Civil Defense Forces, also known as White Helmets, reported that six people were killed, including two children and a woman, and 75 injured in shelling targeting at least six camps west of the capital.
The pro-government Sham FM radio station said Syrian government forces have shelled positions of the al-Qaida-affiliated Hayat Tahrir al-Sham group, the most powerful militant group in Idlib. It said Syrian and Russian warplanes also attacked the areas.
The conflict in Syria erupted in March 2011 and has since killed hundreds of thousands of people, displaced half of the pre-war population of 23 million and devastated large parts of Syria.