Six people were killed after heavy rain triggered flash floods and landslides in a remote corner of India's northeast, officials told AFP Friday.

Another five people were missing around the affected area in Sikkim, a state in the Himalayan foothills bordering China and popular with Indian tourists.

Senior state government official Gopinath Raha said flood waters from the Teesta river had also washed away roads and bridges, temporarily stranding more than 1,500 people.

"The water level of the Teesta river surged past the danger mark on Thursday morning, causing severe damage on the roads and disrupting traffic," he told AFP.

"More than 100 vehicles are struck at various points in the northern part of Sikkim."

Mangan district police superintendent Sonam Dichu told AFP that parts of the state's north had been "cut off from the rest of the country".

"Many houses have been washed away," he added.

Sikkim's state disaster agency said rescue operations were underway but damage to the local mobile phone network was hampering relief efforts.

Sikkim chief minister Prem Singh Tamang said his government was working "to provide every possible support to the victims and affected families".

Flash floods along the river last year, triggered by a glacial lake bursting its banks, dealt extensive damage to roads and bridges across the state.