Majid bin Muhammad al-Majid, suspected leader of the Abdullah Azzam Brigades, in an undated file photo released by the Saudi Interior Ministry.
Majid bin Muhammad al-Majid, a Saudi national who was wanted by authorities in his own country, had been suffering from kidney failure and went into a coma on Friday, the sources said. He died in a military hospital in Beirut, they added.
Majid, who was reportedly apprehended in late December by Lebanese authorities, was believed to be the leader of the Abdullah Azzam Brigades, which have claimed numerous terrorist attacks across the region, most recently the double suicide assault on Iran's Beirut embassy, which killed at least 25 people.
His identity was confirmed by Lebanese officials on Friday after DNA tests.
In tweets at the time of the bombing, the Abdullah Azzam brigades threatened more attacks in Lebanon unless Iran pulled its forces out of Syria.