The US has indications that Russia has begun carrying out airstrikes in Syria, a US official told Reuters on Wednesday, hours after the Russian parliament approved the use of military force in the Middle Eastern country.

The airstrikes appeared to be carried out in the vicinity of Homs, the official said. Russia gave the US advanced notice that it intended to carry out the strikes, the official added.  

The US military's Central Command did not immediately respond to a request for comment.

President Vladimir Putin on Wednesday secured parliament's unanimous backing to launch air strikes against Islamic State militants in Syria.

The move, which sets the stage for Russia's biggest play in the region since the 1991 collapse of the Soviet Union, was announced as Syrian government warplanes conducted heavy strikes in Homs province and the United States and its allies struck Islamic State targets.

Russia, which has been steadily dispatching more and more military aircraft to a base in Latakia, declined to say when it would launch its own strikes, but made it clear it too would be targeting Islamic State militants. 

On Wednesday, Russia reportedly demanded that American warplanes exit Syrian airspace immediately.

A US official told Fox News that Russian diplomats sent an official message to the US ordering American planes out of Syria, adding that Russian fighter jets were now flying over Syrian territory.