Nepal has shut schools for three days after deadly landslides and floods triggered by two days of heavy rain across the Himalayan nation.

The country's Home Ministry said at least 170 people had been killed across the country, with another 42 still missing.

The floods brought traffic and normal activity to a standstill in the Kathmandu valley, where 37 deaths were recorded in a region home to 4 million people and the capital.

Authorities said students and their parents faced difficulties as university and school buildings damaged by the rains needed repair.

"We have urged the concerned authorities to close schools in the affected areas for three days," Lakshmi Bhattarai, a spokesperson for the education ministry, told Reuters.

Some parts of the capital reported rain of up to 322.2mm, pushing the level of its main Bagmati river up 2.2m past the danger mark, experts said.

The Department of Hydrology and Meteorology said preliminary data from stations in 14 districts measured record-breaking rain in the 24 hours to Saturday morning.  

A station at the Kathmandu airport recorded about 240mm of rain, the highest since 2002, it said. 

But there were some signs of respite on Sunday morning, with the rains easing in many places, said Govinda Jha, a weather forecaster in the capital.

"There may be some isolated showers, but heavy rains are unlikely," he said.

'Never seen flooding on this scale' 

Television images showed police rescuers in knee-high rubber boots using picks and shovels to clear away mud and retrieve 16 bodies of passengers from two buses swept away by a massive landslide at a site on the key route into Kathmandu.

Weather officials in the capital blamed the rainstorms on a low-pressure system in the Bay of Bengal extending over parts of neighbouring India close to Nepal.

Deadly rain-related floods and landslides are common across South Asia during the monsoon season from June to September.

But experts say climate change is increasing their frequency and severity.

Climate scientists urge government to step up

Haphazard development amplifies climate change risks in Nepal, say climate scientists at the International Centre for Integrated Mountain Development (ICIMOD).

"I've never before seen flooding on this scale in Kathmandu," said Arun Bhakta Shrestha, an environmental risk official at the centre.

In a statement, it urged the government and city planners to "urgently" step up investment in, and plans for, infrastructure, such as underground stormwater and sewage systems, both of the "grey", or engineered kind, and "green", or nature-based type.

The impact of the rains was aggravated by poor drainage due to unplanned settlement and urbanisation efforts, construction on flood plains, lack of areas for water retention, and encroachment on the Bagmati river, it added.

The level in the Koshi river in Nepal's south-east has started to fall, however, said Ram Chandra Tiwari, the region's top bureaucrat.

The river, which brings deadly floods to India's eastern state of Bihar nearly every year, had been running above the danger mark at a level nearly three times normal, he said.

Humanitarian organisations are also helping with search and rescue operations, as well as providing relief. 

Jagan Chapagain, head of the International Federation of Red Cross and Red Crescent Societies, said in a post on social platform X that staff and volunteers "are distributing non-food items, providing hygiene kits, and setting up evacuation centres".

Reuters/AFP