Turkish fighter jets have forced a Syrian passenger plane suspected of carrying weapons to land in Ankara.
Military communications devices were confiscated, and the Airbus A320 was given permission to leave, reports say.
Turkey's foreign minister said Ankara was determined to stop any transfer of weapons to Syria through its airspace.
Tensions have been high since five Turkish civilians were killed by Syrian mortar fire last week, prompting Turkey to fire into Syria.
It was the first time since the uprising against President Bashar al-Assad began 19 months ago.
Earlier on Wednesday, Turkey's top military commander warned Syria that Ankara would respond with greater force if Syria continued its cross-border shelling.
The Airbus A320 airliner, which was travelling from Moscow to Damascus, was carrying 35 passengers and two crew - far fewer than its 180 passenger capacity.
Turkish Foreign Minister Ahmet Davutoglu told state-run television that Ankara had received information that the plane could be carrying "non-civilian cargo".
The aircraft was escorted by two Turkish jets to the capital's Esenboga airport for security checks.
Local media reports say that military communication devices were seized by the Turkish authorities for further examination and the aircraft was granted permission to leave.
Meanwhile, the Turkish authorities have declared Syrian airspace to be unsafe and are preventing Turkish aircraft from flying over the country.
The BBC's James Reynolds in southern Turkey says that Ankara clearly wants to show its own population and Syria that it is taking the threat posed by Syria extremely seriously.
If weapons are going to Syria, the Turkish government might worry that they will be fired back into its territory, our correspondent says.
Meanwhile, the US has confirmed reports it has established a military task force in Jordan.
It is monitoring the security of Syria's chemical and biological weapons as well as helping with the aid effort.