Landslides, triggered by heavy rains, blocked the National Highway 10, cutting off Sikkim from the rest of the country, officials said on Monday morning.

Personnel of the Border Roads Organisation are clearing the highway at 29 Mile area in West Bengal's Kalimpong where the incident happened, they said.

The debris from the overnight landslide has covered almost 70 m stretch and it will take some time to clear the road for one-way traffic, officials said.

At present, vehicles are being diverted through an alternate narrower and longer road that passes via the Darjeeling hills, they said.

The area, about 60 km from the Sikkim border town of Rangpo, is a trouble spot on the state's lifeline NH-10. It was blocked due to landslides at least four times so far this monsoon.