AVA- At least 49 people have been killed across Nepal and 45 more in neighbouring India in flash flooding and landslides as rescuers search for dozens more missing.

Shankar Hari Acharya, the chief of Nepal's national emergency centre, said on Sunday that thousands were forced to move to higher grounds.

"Search and rescue works are under way but the water levels have not declined yet," he said.

In India, rescuers were trying to reach two packed buses swept into a gorge by a landslide so powerful it destroyed an entire stretch of highway.

The coaches had stopped for a tea break around midnight on Saturday in Himachal Pradesh when tonnes of rock and mud cascaded down a mountainside.

Forty-five bodies have been recovered from the accident site in the Himalayan state, said Sandeep Kadam, a senior government official at the scene.

But more were still missing somewhere at the bottom of the ravine, with soldiers and rescuers clawing through the mud and rock to reach them.

"Around 200 metres of national highway washed away with two buses and more than 50 feared buried," said Colonel Aman Anand, Indian army spokesman, who was helping coordinate rescue efforts.

The disaster followed days of heavy rain, which loosens the soil on steep hillsides and threatens villages at the foot of mountains every monsoon season.

Hundreds have died across India in torrential rain, floods and landslides since the onset of the wet season in April.

In Nepal, the toll from this year's monsoon - which typically lasts from late June until the end of August - has already surpassed that of last year, with more than 100 people confirmed dead.

Al Jazeera's Subina Shreshtha, reporting from Janakpur in Nepal, said the area swamped by floods was knowsn as the bread basket of Nepal.

"Some 80 percent of the crops have been damaged. It's going to have a huge impact in the long run for the country."

This year's flooding has been exacerbated by dams built on the India-Nepal border, she said, adding, "A lot of water that used to go to India has been blocked. So a lot of this damage has been man made."