The Washington Post reports: Russia demanded an explanation from Turkey on Thursday for why it intercepted a Syrian passenger plane flying from Moscow to Damascus, the latest instance of spiraling Syrian-Turkish tensions related to Syria’s bloody civil war.

Turkey said it used F-16 fighter jets to force the Syrian Airbus to land at Esenboga Airport in Ankara in order to seize equipment that it believes was destined for use by the Syrian military against the armed, anti-government rebels.

Syrian Transport Minister Mahmoud Said said the move amounted to “air piracy,” Reuters quoted the state-controlled television news as saying. The comments exacerbated the already tense back-and-forth between Turkey and Syria following a Syrian mortar strike that killed five civilians in a Turkish border village last week.

The Airbus 320, with 30 passengers on board, was intercepted as it entered Turkish airspace shortly after 5 p.m. local time on Wednesday (10 a.m. in Washington). Hours earlier, Turkey had ordered all Turkish civilian aircraft to cease flights through Syrian airspace, apparently to prevent Syria from taking reciprocal action.

Turkish Foreign Minister Ahmet Davutoglu told Turkish television network TGRT that the plane had been forced down because it was carrying “non-civilian cargo” and “banned material.”

“There is information that the plane had cargo on board that does not meet the requirements of civil aviation,” Davutoglu said. The Today’s Zaman newspaper later reported that Turkish authorities found military communication equipment and “parts that could be used in missiles” on the plane.