Saudi Arabia has been supplying Syrian rebels with arms bought from Croatia, according to The New York Times.
The newspaper is reporting they have been buying the weapons used during the Balkan wars of the 1990s.
Rebels have been fighting President Bashar al-Assad's regime since an uprising against his rule erupted in March 2011.
The United Nations estimates the fighting has claimed 70,000 lives.
Yesterday, the Syrian opposition cancelled a planned boycott of an international conference on the conflict, to be held in Rome later this week, after appeals from Britain and the United States.