al Qaeda in Syria, in the country's rebel-held Idlib province
US Central Command said the operation had targeted those "responsible for attacks." threatening US citizens, our partners and innocent civilians ".
There were 40 people killed in a missile strike on a jihadist training camp.
It was hit in idlib by Syrian government forces.
Unilateral ceasefire, which started at 06:00 (03:00 GMT ).
In a separate development, Turkey warned that it would launch a "safe zone" operation in north-eastern Syria.
"Within a few "Turkish President Recep Tayyip Erdogan said."