It said they were hidden in a coffee shipment destined for Saudi Arabia through Jordan.
The seizure of the drug is one of the largest in Lebanon in recent months. In June, Lebanese authorities seized 250,000 Captagon pills hidden in water pumps, also intended for Saudi Arabia.
In April, Saudi Arabia seized 5.3 million Captagon pills at the port of Jeddah, hidden inside Pomegranates that had been shipped from Lebanon.
The kingdom subsequently banned agricultural imports from Lebanon amid concerns that Lebanese authorities were unable to stop the smuggling of the drug.
Most recent shipment of pills was confiscated last week during raids on a warehouse in Bir Hassan, a suburb in southern Beirut, the ISF said on Twitter.
It said it had arrested two men, one of whom tried to fly out of the country.
A video it posted online showed a man ripping open a coffee sack stuffed with pills.
Syria drug raid
In a separate operation, Syrian authorities seized “hundreds of thousands” of Captagon pills in the southern province of Deraa, the official Sana news agency said, citing a security source.
“The drugs were to be smuggled abroad via the Jordan border,” Sana said.
It said some arrests were made amid attempts to clamp down on remaining members of the smuggling network.
Captagon was a brand name of the amphetamine-derived stimulant fenethylline and continues to be manufactured, mostly in Lebanon and Syria, for illegal recreational use. Most ends up in Saudi Arabia.
According to an EU-funded report by the Centre for Operational Analysis and Research, “Captagon exports from Syria reached a market value of at least $3.46 billion” in 2020.
In July last year, Italy seized a record 14-tonne haul of the drug – or 84 million pills – that had arrived from Syria.