At least one person died and seven others were missing after houses and bridges were washed away when a river burst during heavy monsoon rains in Nepal, officials said Wednesday.

The annual monsoon rains in the Himalayan nation revitalises farms and waterways but also triggers deadly landslides and floods.

Officials said a landslide caused by the monsoon deluge blocked a river, which then burst and sent a flood of water downstream late Tuesday, inundating a settlement in Sindhupalchowk district near the capital Kathmandu.

"One body has been recovered and seven others are missing from different places in the flood," district official Baburam Khanal told AFP.

Rescuers from the police and army rescued at least 60 people, officials added, using helicopters for difficult-to-reach areas.

The river started swelling suddenly on Tuesday evening, locals told AFP.

"None of the residents have slept tonight, we haven't slept at all looking at this terrifying situation," resident Sailesh Khadka said.

"It all happened after 8pm or 9pm at night."

A further two people died and four others remained missing after flooding in other districts over the past two days, Dil Kumar Tamang of Nepal's National Emergency Operation Center said.

"We are also sending relief materials to the affected but the weather is making the process difficult," Tamang said.

Heavy rains were forecast for at least the next two days, the weather bureau said.

The number of deadly floods and landslides has increased in recent years in Nepal. Experts say climate change and more road construction could be triggering the deadly disasters.

More than 200 people were killed in landslides and floods in Nepal during last year's monsoon season.