The U.S. military said on Wednesday it was removing 12 fighter jets from Incirlik air base in Turkey after sending them there last month to bolster the fight against Islamic State and to help reassure Turkey after Russian incursions its airspace.
Russia's violation of Turkish airspace over the weekend "does not look like an accident", Nato has said.
Secretary-General Jens Stoltenberg said Russia had not provided "any real explanation" of the violation, which "lasted for a long time."