Moscow: Russia launched its first air strikes in war-torn Syria on Wednesday after President Vladimir Putin won parliamentary permission to use force abroad.
It was Moscow's first military engagement in a distant theatre of war since the Soviet invasion of Afghanistan in 1979.
Putin said the action was pre-emptive, warning that Moscow would be hunting down Islamic State militants before they target Russia.
"The only correct way to fight international terrorism... is to act preemptively, to battle and destroy fighters and terrorists on the territories they have already seized, not to wait for them to come to us," Putin said in televised comments.
The Russian defence ministry said Moscow had launched targeted air raids against the "terrorists" in Syria.
A Syrian security source said the war planes hit three provinces.
The strikes came as Putin and US President Barack Obama push rival plans on ways to defeat the Islamic State group in Syria and on the future role of the country's embattled leader Bashar al-Assad.
"They gave us a heads-up they were going to start striking in Syria," a US defence official said. "It was in the vicinity of Homs."
Putin had just hours earlier won permission from the upper house of parliament, the Federation Council, to deploy troops abroad.
"The Federation Council unanimously supported the president's request," Kremlin chief of staff Sergei Ivanov said.
He said the decision was taken after Assad asked Russia for military support, a request confirmed by Damascus.
Ivanov, a former defence minister, declined to give details of the operation, saying only it would be limited in duration and ruling out ground operations by Russian troops.
Putin is seeking to muscle his way back onto the world stage after months of Western isolation following Russia's seizure of Crimea from Ukraine and support for a separatist insurgency in the east of the ex-Soviet country.
Addressing the UN General Assembly for the first time in a decade, Putin on Monday proposed a broad UN-backed coalition to fight IS militants and clashed with Obama on the future of Assad.
Washington and its allies blame Assad for the mayhem in Syria, where four years of bloodshed have killed more than 240,000 people.