The announcement comes as Putin and US President Barack Obama are pushing rival plans on ways to defeat the Islamic State group in Syria and the role of the country's embattled leader Bashar al-Assad.
"The Federation Council unanimously supported the president's request," the Kremlin's chief of staff Sergei Ivanov said in televised remarks after the upper house approved Putin's request to deploy troops abroad.
"We are talking about Syria," he said, adding that the decision to launch air strikes was taken after the Syrian president asked Russia for military support.
Putin is seeking to muscle his way back onto the world stage after months of Western isolation after Russia's seizure of Crimea from Ukraine and support for a separatist insurgency in the east of the ex-Soviet country.
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At the United Nations on Monday, the Russian strongman proposed a broad UN-backed coalition to fight IS militants and clashed with Obama on the future of Assad.
France, meanwhile, has launched a probe into Assad's regime for alleged crimes against humanity, a judicial source said. Prosecutors opened a preliminary inquiry on September 15 into alleged crimes committed by the Syrian government between 2011 and 2013, the source told AFP in Paris.
The Syrian Observatory for Human Rights monitoring group said that France's first air strike on the Islamic State group killed at least 30 jihadists, including 12 child soldiers.
President Francois Hollande said Sunday that six French warplanes hit an IS training camp near Deir Ezzor city, and that more strikes could follow in the coming weeks.
For its part, Russia argues that the West should support Assad in his fight against the jihadists, but Obama said at the United Nations on Monday that the Syrian leader must go if the Islamic State group is to be defeated.
Moscow already has a powerful military detachment on a Syrian airbase in government-held territory, equipped with warplanes and tanks, and will now work more closely with neighbouring Iraq.