British troops are to be deployed to the Baltics as part of a long-term Nato mission to deter Russian aggression.
Defence Secretary Michael Fallon said a "small number" of soldiers would be stationed there to "watch over our allies on the eastern borders".
RAF Typhoon fighters are already in the region as part of the Baltic Air Policing detachment and have been called into action in recent months.
Turkish Prime Minister Ahmet Davutoglu has said Turkey "will not compromise" on the security of its airspace and warned further violations by Russian warplanes will be viewed as a threat.
Davutoglu issued the warning during a live state TV broadcast today after it was revealed Russian warplanes violated Turkey's airspace for a second time on Sunday.
Despite the warning the PM has said he does not want conflict in Syria to turn into a crisis between Russia and NATO, or escalate into a Russian-Turkish dispute, and said an offer by the Russians to "meet and discuss the issue" has been welcomed.
Incursions by Russian jets into Turkish airspace have prompted a stern response from Nato's most powerful ally.
Here's what you need to know about this latest development in the increasingly bloody, complicated and volatile conflict.
Russia urges world leaders to unite to fight terrorism in Syria amid criticism that air strikes have targetted rebel fighters and civilians.