Russia has begun carrying out air strikes in Syria against Isis in Syria.
The strikes reportedly hit rebel-controlled areas of Homs and Hama provinces, causing casualties.
The US says it was informed an hour before they took place.
Russian defence officials say aircraft targeted the Islamic State group, but an unnamed US official told Reuters that so far they did not appear to be targeting IS-held territory.
The upper house of the Russian parliament granted President Vladimir Putin permission to deploy the Russian air force in Syria.