Russia says a Syrian plane intercepted by Turkey on Wednesday was transporting a legal shipment of radar equipment.
Foreign Minister Sergei Lavrov said on Friday there were no weapons on the plane.
There were heated exchanges on Thursday between Turkey and Syria over the exact nature of the confiscated items.
The BBC reports Damascus has challenged Ankara to put the seized goods on public view.
The Syrian Air plane was intercepted by Turkish fighter jets en route from Moscow to Damascus on Wednesday, and forced to land in Ankara.
Prime Minister Recep Tayyip Erdogan said Russian defence equipment was found on board.
The BBC reports Russia is an ally of the Syrian government, whereas Turkey has been a critic of President Assad since anti-government protests began there more than a year ago.