Fighting appeared to have stopped temporary as the ceasefire in Syria held for one day, with only minor violations reported.
No civilian deaths were reported for 15 hours of the ceasefire, the UK based group, the Syrian Observatory for Human Rights reported.
UN aid convoys however were kept on standby however, until a more definitive truce could be assured.
The ceasefire follows an agreement between Russia and the USA on Friday in Genenva after several months of negotiations.
If the ceasefire is maintained for seven days US and Russian jets will conduct air strikes on Islamic State and associated groups.