BBC News has uncovered evidence that appears to suggest that weapons intended for the Saudi military have been diverted to Syrian rebels.
Three crates from an arms manufacturer – addressed to Saudi Arabia – have been seen in a base being used by rebel fighters in the city of Aleppo.
How the small crates reached Aleppo is unknown, and the BBC was not allowed to film their contents.
Saudi Arabia has refused to comment on the matter.
Turkey is calling for “international action” on Syria after a sixth consecutive day of cross-border shelling.
Turkey returned fire across the border on Monday after a Syrian shell fell on its territory.
Turkey would continue to do everything necessary to protect its borders, President Abdullah Gul said on Monday, adding that the “worst-case scenarios” were now taking place in Syria.