Syria crisis: Nato to discuss Russia air campaign
Russia's growing military involvement in the Syria conflict is expected to be high on the agenda of Nato defence ministers meeting in Brussels, the BBC reported.
It comes after Nato member Turkey said Russian jets had violated its airspace.
Russia has fired missiles from a warship in addition to air strikes to support Syrian leader Bashar al-Assad.
But Moscow denies Western accusations that its strikes have mainly hit Assad opponents, some supported by the West, and not Islamic State (IS) militants.
BBC defence correspondent Jonathan Marcus says Nato aims to make clear it will respond to any challenge.