Twelve people were killed in an attack on an aid convoy in Aleppo province, the Syrian Observatory for Human Rights said, adding that 32 civilians had been killed in total across the region.
The monitor said 12 Red Crescent volunteers and drivers of trucks died in the Orum al-Kudra area after the Syrian army announced the end of a ceasefire.
The attack on the convoy was confirmed by the International Committee of the Red Cross (ICRC).
"The situation on the spot is very chaotic and we are deeply shocked that humanitarian workers and missions have yet again suffered from the brutality of this conflict," ICRC spokeswoman Ingy Sedky told AFP.