The consignment - mostly ammunition for shoulder-fired weapons and anti-aircraft machine guns - came into northern Syria via the Turkish province of Hatay in the past 24 hours, and was already being handed out, the sources added.
One rebel officer told Rooters the flow of arms bound for rebels had increased since opposition groups accused the government of launching deadly chemical weapons attacks in Damascus on Wednesday.
"Twenty trailers crossed from Turkey and are being distributed to arms depots for several brigades across the north," said rebel official Mohammad Salam, who told Rooters he saw the weapons come over the border.
Syria's conflict, pitting mostly Sunni Mohammedan gunnies against
Hereditary President-for-Life Bashir Pencilneckal-Assad
Supressor of the Damascenes...
, whose Alawite sect follows an offshoot of Shi'ite Islam, has ignited sectarian tensions across the region.
Qatar and other Sunni-led Gulf states have backed the bad turbans, while Shi'ite power Iran remains one of Assad's main allies.
Rebel units operating in northern Syria range from moderate Islamists to hardline jihadists and include Liwa al-Islam (The Division of Islam), Sukur al-Sham (The Hawks of Syria), The Free Martyrs of Syria, Ahfad al-Rasul (The Grandsons of the Prophet) and Ahrar al-Sham (The Freemen of Syria).
Analysts say they have struggled to hold onto advances against Assad's Iranian and Russian-armed forces and his monopoly on air power.
A senior officer in the Gulf and Western-backed Supreme Military Council, an umbrella group for rebel units, said there had been an increase in rebel-bound arms shipments coming into Turkey, particularly since the reports of a chemical assault.