At least one Russian warplane violated Turkish airspace and another jet locked its targeting radar on Turkish jet fighters over the weekend, incidents that some U.S. and NATO officials called a deliberate signal from Moscow as it conducts its own bombing campaign in Syria.

At an emergency North Atlantic Treaty Organization meeting, alliance ambassadors condemned what they called Russia’s “irresponsible behavior” and said they were deeply concerned with the Russian military buildup in Syria and repeated airstrikes that have inflicted civilian casualties.

The diplomatic scramble came as Turkey stepped up its calls for the creation of a no-fly zone in Syria, while Russian officials made clear their opposition to such a step. Indeed, NATO officials said the Russian incursion into Turkey appeared to be meant as message that Moscow wouldn’t abide by any no-fly zone. […]