The drug, in the form of 84 million Captagon tablets, was worth about one billion euros, police said in a statement, describing the operation as "the biggest seizure of amphetamines in the world".
"We know that the Daesh finances its terrorist activities mainly by trafficking drugs made in Syria which in the past few years has become the world's largest producer of amphetamines," the statement added, AFP reported.
The shipment was hidden in three containers found in the port of Salerno, just south of Naples.
Captagon, a brand name, was originally for medical use but illegal versions have been widely used by Daesh terrorists in combat -- the police said.