Acting on specific inputs, security personnel intercepted the truck, carrying arms and ammunition, at Khetri in Assam's Goalpara district at around 1 AM, they said, adding the vehicle was on its way towards Mendipathar in Meghalaya's North Garo Hills district.
The truck had taken off from Dimapur in Nagaland, passed through Guwahati before it was held and seized at Khetri, they said.
On detail checking of the truck, one AK 56 rifle, one .303 rifle, a shotgun and a .22 rifle was seized from the truck, police said, adding that 354 ammunition of 7.62 rifle, 122 AK rifle ammunition and 33 shotgun ammunition were seized, the sources said.
In the post seizure operations, police have arrested three arms dealers involved in the case - one from Guwahati and the other two from Tura.
The GNLA is an outlawed militant organisation which is active in all five western Garo Hills districts in Meghalaya and had been involved in kidnapping, extortion and killing of both civilian and security forces involved in counter insurgency operations.