Separate weather systems brought torrential, extended rainfall to the entire island of Sri Lanka and large parts of Indonesia's Sumatra, southern Thailand and northern Malaysia last week.

Arriving in North Sumatra on Monday, Indonesia President Prabowo Subianto said the government's "priority now is how to immediately send the necessary aid."

"There are several isolated villages that God willing, we can reach," he added, saying the government was deploying helicopters and aircraft to aid the relief effort.

Prabowo has come under increasing pressure to declare a national emergency in response to flooding and landslides that have killed at least 442 people, with hundreds more missing.

Unlike his Sri Lankan counterpart, he has also not publicly called for international assistance.

The toll is the deadliest in a natural disaster in Indonesia since a massive 2018 earthquake and subsequent tsunami killed over 2,000 people in Sulawesi.

The government has sent three warships carrying aid and two hospital ships to some of the worst-hit areas, where many roads remain impassable.

- Sri Lanka seeks aid -

In Sungai Nyalo village, about 100 kilometres (62 miles) from West Sumatra's capital Padang, floodwaters had mostly receded on Sunday, leaving homes, vehicles and crops coated in thick grey mud.

"Most villagers chose to stay; they didn't want to leave their houses behind," said Idris, 55, who, like many Indonesians, goes by one name.

In Sri Lanka meanwhile, the government called for international aid and used military helicopters to reach people stranded by flooding and landslides triggered by Cyclone Ditwah.

At least 334 people have been killed, Sri Lanka's disaster agency said on Sunday, with many more still missing.

Officials said the extent of damage in the worst-affected central region was only just being revealed as relief workers cleared roads blocked by fallen trees and mudslides.

President Anura Kumara Dissanayake, who declared a state of emergency to deal with the disaster, vowed to build back.

"We are facing the largest and most challenging natural disaster in our history," he said in an address to the nation.

"Certainly, we will build a better nation than what existed before."

The losses and damage are the worst in Sri Lanka since the devastating 2004 Asian tsunami that killed around 31,000 people and left more than a million homeless.

- Anger in Thailand -

By Sunday afternoon, rain had subsided across Sri Lanka but low-lying areas of the capital were flooded and authorities were bracing for a major relief operation.

Military helicopters have been deployed to airlift stranded residents, and deliver food, though one crashed just north of Colombo on Sunday evening.

Selvi, 46, a resident of the Colombo suburb of Wennawatte, left her flooded home on Sunday, carrying four bags of clothes and valuables.

"My house is completely flooded. I don't know where to go, but I hope there is some safe shelter where I can take my family," she told AFP.

Much of Asia is currently in its annual monsoon season, which often brings heavy rain, triggering landslides and flash floods.

But the flooding that hit Indonesia, Thailand and Malaysia was also exacerbated by a rare tropical storm that dumped heavy rain on Sumatra island in particular.

Climate change has also increased the intensity of storms, and produced more heavy rain events because a warmer atmosphere holds more moisture.

The waves of rain caused flooding that killed at least 176 people in southern Thailand, authorities said Monday, one of the deadliest flood incidents in the country in a decade.

The government has rolled out relief measures, but there has been growing public criticism of the flood response, and two local officials have been suspended over their alleged failures.

Across the border in Malaysia, where heavy rains also inundated large stretches of land in Perlis state, two people were killed.

burs-sah/tc