Floods and landslides caused by torrential monsoon rains have killed at least 50 people across Nepal while dozens more are missing, officials said on Sunday.

Northeast India has also been hit by floods with 11 deaths recorded as rivers burst their banks.

Residents walk towards dry ground from a flooded colony in Kathmandu, Nepal, on Saturday. Navesh Chitrakar/Reuters

Heavy rains since Thursday have hit several districts in Nepal, especially in the country's eastern region and the southern plains, affecting thousands.

Nepal police spokesman Bishwaraj Pokharel said 33 people are missing while over 1,100 people have been rescued.

"We have mobilised all resources in the country for search, rescue and relief and have been able to reach all affected areas," Pokharel told AFP.

Authorities said river levels are expected to return to normal from Monday.

Monsoon rains from June to September cause widespread death and destruction across South Asia each year.

In India at least 11 people have died in the country's northeast, officials said, with some 20,000 being housed in relief camps in badly-hit Assam state.

In Bangladesh aid groups were providing rations to Rohingya refugees in the southeast of the country with the UN World Food Programme saying on Friday that two people including a child had died.

Last year, more than 1,200 people were been killed across South Asia in monsoon storms, with India's Kerala suffering its worst floods in nearly 100 years.

Workers were also repairing fallen communication towers to restore phone lines.

Twenty-eight people have been treated for injuries and more than 1,100 others rescued from flooded areas. More than 10,000 people are estimated to have been displaced.

Nepal's Department of Hydrology and Meteorology warned of more troubles ahead in a flood warning for the southern region near the main rivers, urging people to keep watch on rising water levels and move to higher grounds when needed.

Rain-triggered floods and mudslides have left a trail of destruction in other parts of South Asia. Officials in northeastern India have reported at least a dozen people dead and over a million affected.

The dead included two schoolchildren who were buried when their boarding school collapsed while they were asleep in Tawang in Arunachal Pradesh state.

Assam's State Disaster Response Authority said around 900,000 people spread over 21 of the state's 33 districts have had their homes submerged. Several thousands are living in government-run relief camps.

Agencies