Since the beginning of 2019, at least 173 civilians, including 41 children, have died from anti-personnel mines and explosives from the war, the Observatory said in a written statement.
At least 40 of the victims were killed by explosives while searching through the ruins.
According to the United Nations, 10.2 million men, women and children in Syria are under threat of unexploded devices.
"Every day civilians are killed or disabled for life due to anti-personnel mines and unexploded devices", the UN Humanitarian Coordination Bureau said recently.
A UN spokesman said in August in Damascus that explosives prevented people from returning to their homes, removing debris and rebuilding them, as well as preventing their land from being safe again.