Turkish fighter jets have forced a Syrian passenger plane suspected of carrying weapons to land in Ankara.
Military communications devices were reportedly confiscated before the plane was allowed to leave hours later.
The Airbus A320 airliner was travelling from Moscow to Damascus with 35 passengers - far fewer than its 180 passenger capacity - and two crew.
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 for 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.
Ankara had received information the Damascus-bound plane plane could be carrying "non-civilian cargo", Turkish Foreign Minister Ahmet Davutoglu told state-run television.
"We are determined to control weapons transfers to a regime that carries out such brutal massacres against civilians," said Mr Davutoglu. "It is unacceptable that such a transfer is made using our airspace.
"Today we received information this plane was carrying cargo of a nature that could not possibly be in compliance with the rules of civil aviation."
The aircraft was escorted by two Turkish jets to the capital's Esenboga airport for security checks.
Military communication devices were seized by the Turkish authorities for further examination, local media reports said.
The aircraft was allowed to take off at 02:30 (23:30 GMT on Wednesday), after several hours on the ground.
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 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.