The death toll due to flooding and landslides across Nepal since Friday reached 49, officials said.
The home ministry has been approached for help, said an hotelier.
Police said they recovered six bodies.
Dozens of elephants and rafts have been deployed to rescue almost 500 people trapped by floods in a popular resort in southern Nepal, officials say.
Meanwhile, many highway bridges which serve as the lifeline of the nation have been damaged, obstructing vehicular movement for relief and rescue programmes.
The Meteorological Forecasting Division has forecast moderate to heavy rains to continue across the country for the next few days.More news: Trump to order investigation into China's trade practice
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Thousands of houses have been inundated.
The monsoon season, which starts in June and ends in September, causes big floods in Nepal each year.
Families perched on trees with young children overnight as flood waters swept away homes in a village in the southern district of Chitwan, local media reported.
In the popular jungle safari resort of Sauraha in Chitwan, hotels were forced to shift their guests to higher floors as waters rushed into the premises. In the eastern city of Biratnagar an airport runway was under two feet of water, TV footage showed, leading to a suspension of flights.
The Department of Hydrology and Meteorology said further heavy rains were expected on Sunday in the country's central and mid-western regions.
"I have already instructed authorities concerned to rescue flood victims, move them to safer locations and immediately provide relief to them", Prime Minister Sher Bahadur Deuba said in a video recording Saturday.