Turkey scrambled fighters and briefly detained a Syrian passenger plane, suspecting it of carrying military equipment from Moscow.
Military jets escorted the Damascus-bound Airbus A-320, carrying around 30 passengers, into the airport in Ankara.
The move came hours after Turkey's chief of staff said his troops would respond with greater force if bombardments from Syria kept hitting Turkish territory, state TV said.
Separately, Foreign Minister Ahmet Davutoglu said they had received information the plane was carrying cargo “of a nature that could not possibly be in compliance with the rules of civil aviation”.
Turkish authorities had seized some of the cargo and the plane and its passengers would be allowed to continue their journey to Damascus.
Mr Davutoglu said Turkey was within its rights to investigate planes suspected of carrying military materials but declined to say what was in the seized cargo.
Turkey would continue to investigate Syrian civilian aircraft using its airspace, Mr Davutoglu said.
He also said Syrian airspace was no longer safe and that Turkish passenger planes should not fly there.
More than 18 months into the battle for Syria, an estimated 30,000 people are dead and the country is disintegrating.
Rebels are outgunned by the government but can still strike at will, and President Bashar al-Assad has assumed personal command of his forces.
A sharp rise in casualties in Syria in the past month indicates the growing intensity of the conflict, which spiralled from peaceful protests against Mr Assad's rule in March 2011 into a full-scale civil war.
The Syrian government said on Wednesday that an appeal by UN Secretary General Ban Ki-moon for a ceasefire was only acceptable if the rebel forces agreed to abide by it too.
