At least 63 people were missing in Nepal on Friday after a landslide triggered by heavy monsoon rains swept two buses off a highway and into a river, authorities said.

Dozens of search and rescue personnel were combing the site for survivors of the accident in the central district of Chitwan, district official Khimananda Bhusal told AFP.

Bhusal said that the buses were carrying at least 66 people between them but three passengers had been able to escape before they crashed into the Trishuli river and were now being treated in hospital.

“We are not sure of the total number because the buses could have picked up others on the road,” he said. “The river has swollen and no one else has been found yet.”

The accident took place along the Narayanghat-Mugling highway, around 100 kilometres west of the capital Kathmandu early Friday at 3:30am local time.

One bus was heading from the capital Kathmandu to Gaur in Rautahat district in southern Nepal and the other was en route to Kathmandu from southern Birgunj.

A driver was killed in a separate accident on the same road after a boulder hit his bus. He died as he was being treated at a hospital.

Prime Minister Pushpa Kamal Dahal expressed sadness over the accident in a post on social media platform X. “I direct all agencies of the government, including the home administration, to search for and effectively rescue the passengers,” he said.

Deadly crashes are common in the Himalayan republic because of poorly constructed roads, badly maintained vehicles and reckless driving. Nearly 2,400 people lost their lives on Nepal’s roads in the 12 months to April, according to government figures.

Twelve people were killed and 24 were injured in an accident in January when a bus heading to Kathmandu from Nepalgunj fell into a river.

Road travel becomes deadlier during the annual monsoon season as rains trigger landslides and floods across the mountainous republic.

Monsoon rains across South Asia from June to September offer respite from the summer heat and are crucial to replenishing water supplies, but also bring widespread death and destruction.

The rainfall is hard to forecast and varies considerably, but scientists say climate change is making the monsoon stronger and more erratic.

Floods, landslides and lightning strikes have killed 88 people across the country since the monsoon began in June, according to police figures.