Nato defence ministers will assess the "troubling escalation of Russian military activities" in Syria, the alliance's secretary-general says, ahead of talks in Brussels.
Jens Stoltenberg says he is concerned about Russia's use of cruise missiles as well as air strikes, and that Nato is ready to defend all allies.
Nato member Turkey says Russian jets have violated its airspace recently.
Mr Stoltenberg urged Moscow to stop backing Syrian leader Bashar al-Assad.
Moscow denies Western accusations that it has mainly targeted Assad opponents, insisting its strikes have hit Islamic State (IS) infrastructure, and other militant groups.
IS militants have seized swathes of territory in Syria and Iraq.