Russian President Vladimir Putin defends Russia's military operations in Syria, saying the aim is to "stabilise the legitimate authority" of Syrian President Bashar al-Assad.

Turkey again summons the Russian ambassador after a second violation of its airspace by a Russian warplane operating in Syria in two days.

Turkish F-16 fighter jets are scrambled after a Russian warplane violates Turkey's air space on Saturday, the foreign ministry says.

President Vladimir Putin secures parliament's unanimous backing to launch air strikes against Islamic State militants in Syria, paving the way for imminent Russian military intervention in its closest Middle East ally.