Flooding in Nepal and neighbouring India has killed more than 100 people, and left dozens missing, according to reports.
The death toll in Nepal, where the worst-hit region is eastern Sindhupalchowk, is 118.
About 200,000 people are reported to have been displaced and more than 120 people are missing.
India’s state of Bihar is also affected, with about 40 people reported dead.
‘Unprecedented… tidal wave’
Kumar Man Pokhrel, the head of the United Nations disaster-response agency, Oxfam, told the BBC his organisation was helping distribute drinking water and food in the north-eastern district of Jagatsinghpur.
The BBC’s Charles Haviland in Kathmandu said the scale of the tragedy was the worst he had ever seen.
Prime Minister K P Oli – who was in Paris for a summit with world leaders – has ordered an inquiry into the disaster, and has said it will be investigated “day and night”.
Officials in Nepal told the BBC hundreds of thousands of acres of farmland had been ruined, adding the disaster was the worst the country had ever experienced.
But a spokesman for the India Meteorological Department said despite heavy rains starting just before midday on Monday the country’s largest rivers have been kept at manageable levels.
He said in the southern state of Andhra Pradesh 70 people have died.
Officials in neighbouring Bihar state also said 12 people have died and dozens are missing.
“The tributaries of the Ganges breached their banks, resulting in flood waters inundating over 500 villages in 12 districts,” said the Bihar government.
The Met Office in New Delhi, India, has issued a severe rainfall warning as rivers overflow their banks and spread down to low-lying areas, according to reports in state-run NDTV.
It has also reported heavy rain affecting swathes of northern Andhra Pradesh, Orissa, Gujarat and Punjab.
Power lines have reportedly been swept away or snapped, causing a power outage across northern India.
#WATCH: Flood survivors wade through water, toss mud into river after the rivers overflowed following heavy rain in Chandauli district of Uttar Pradesh. https://t.co/KZbfEJaXYF pic.twitter.com/wzFqeBVj6s — NDTV (@ndtv) March 2, 2018
Cyclone Mora to the north-east
In Sri Lanka, more than 140 people were killed after Cyclone Mora hit the northern region of the island earlier this week.
Almost 6,000 people have also been left homeless, mostly in the east of the country, and thousands of homes have been severely damaged.
In Vietnam, officials say at least nine people have died after Tropical Storm Joyce hit.
The storm is expected to peter out over China in the next few days, according to reports.
Power has been cut in large parts of Vietnam, including its capital Hanoi, on its east coast.
Resident Ngoc Ngoc Ngoc told the Reuters news agency: “We are surrounded by water. It’s really terrifying.”
A US naval ship has been sent to help villagers in Cambodia as that country prepares for what is forecast to be a storm in the coming days.
Cyclone Mekunu is expected to hit the Tonle Sap lake in southern Cambodia, and a “weather warning” has been issued as a precaution.
In January, India and Myanmar’s border states were lashed by the worst monsoon floods in nearly a decade, killing at least 96 people.
After years of neglect in both India and China, civil servants have put emergency response plans in place.