Despite receiving more ammunition from Russia and Iran, Syria is running out of aerial bombs and resorting to improvisations. Thus Syrian helicopters have been seen dropping barrels filled with flammable liquids and explosives, rigged to explode when they hit the ground. This sort of thing is not unique to Syria and has been seen for years in Sudan where the government uses “barrel bombs” rolled out of transports and helicopters. These are not precision weapons, but if the target is a village or other residential area, they are accurate enough.
Moreover, using this approach there is no need for trying to find someone willing to sell you aircraft bombs, which may not be practical because of international arms embargoes. Both Syria and Sudan are under such embargoes. The barrel bombs are easy to build locally from components that are legal to import or fabricate locally.