The highway links last Indian border post on Indo-China border at Lipulekh with the rest of the country.
The agitators alleged that the Border Roads Organisation (BRO) had been neglecting the road despite its importance in guarding the borders.
"It is due to the negligent attitude of BRO, our soldiers have to track five days to reach the last border post from this road, which too is ill-maintained and incomplete," said a protester.
He said the people have come out in support of the bandh and offices and business set-ups were closed in Banbasa, Tanakpur, Champawat, Lohaghat Pithoragarh, Kanalichina Jauljibi and Dharchual and Baluakot towns along the highway.
The organisations also demanded a CBI inquiry into the working of BRO and lodging of criminal cases against it for deaths due to landslides on the highway.