"The Drug Combating Department in the Riyadh region, in cooperation with the customs at the dry port in Riyadh, foiled an attempt to smuggle 5200kg of hashish into the kingdom," the newspaper Arab News quoted the department's director as saying on Tuesday.
Eight suspects, seven from an east Asian country and one Arab, were arrested on Monday as they attempted to receive the cargo at a warehouse, said Major General Uthman al-Assaf.
Another three suspected of taking part in the operation were arrested later, he added.
"The drug consignment contained 5291kg of hashish, which is the largest quantity of drugs ever seized in the history of the kingdom of Saudi Arabia," the official said.
Saudi Arabia applies a strict form of sharia, or Islamic law, and convicted drug traffickers can face beheading.