Two Pakistanis and six Syrians were arrested in a raid on Wednesday.

The arrests took place after the pills, concealed in a flour shipment, arrived at a dry port in Riyadh and were taken to a warehouse, Geo TV quoted the Saudi Press Agency as saying.

A spokesman for the Saudi General Directorate of Narcotics Control said it was the "biggest operation of its kind to smuggle this amount of narcotics into Saudi Arabia in one operation", the agency said.

The report did not specify whether the pills were captagon -- the amphetamine wreaking havoc across the Middle East -- nor did it say where the pills came from.

Captagon pills are produced mainly in Syria and smuggled to large consumer markets in the Gulf.

Trade in captagon in the Middle East grew exponentially in 2021 to top $5 billion, posing an increasing health and security risk to the region, a report by the New Lines Institute said in April, the report said.

Saudi Arabia is the biggest captagon market, and the kingdom´s customs body seized 119 million of the pills last year.