The drugs had passed through the Togolese port of Lome before being transported by truck north to the Nigerien capital Niamey, over 1,000 km (621 miles) and two border crossings away, said spokesman Adili Toro.
The haul was seized on March 2 from warehouses in Niamey. The traffickers had planned to transport the drugs in trucks to Libya via the desert town of Agadez, a hub for smuggling goods and migrants across the Saharan desert.
It is the largest cannabis seizure in Niger's history and the first shipment of drugs known to have come from Lebanon, Toro said by phone.
Police have arrested 11 Nigeriens and two Algerians in Niamey and Agadez in connection with the case, he said.
The West African Atlantic Coast region is seen as a frequent stopping point for drugs including cocaine and cannabis from South America and elsewhere heading to North Africa and Europe.Ivory Coast security forces seized just over 1 ton of cocaine in the commercial capital Abidjan in February.