Monsoon rains have claimed hundreds of lives across Asia, authorities reported Monday, as rescuers scrambled to reach remote areas of India, Pakistan and Myanmar after flash floods and landslides.

Authorities in India say more than 120 people have died across the country in recent days, while more than a million have been displaced by rains worsened by a cyclone that barrelled through the Bay of Bengal last week.

On Monday rescuers resumed their search for villagers after downpours caused a landslide in India's remote northeastern state of Manipur, where an official said four bodies have so far been recovered from a hamlet buried by a collapsed hill.

In neighbouring Myanmar heavy seasonal rains -- augmented by Cyclone Komen -- have killed 46 people so far and affected more than 200,000, with swathes of the country hit by rooftop-high floods.

The government has designated four "national disaster-affected regions" in central and western Myanmar, where villagers have been forced to use canoes and makeshift rafts to escape the rising waters.

Thousands of others are already in camps for the displaced including in the Kalay district of Sagaing region, where residents told of unusually powerful floodwaters swamping homes in hours.

"We've lost all that we have. Our house is still under water," Htay Shein, 62, told AFP from a temporary shelter in Kalay.

"We have seen floods, but never anything like this before."

An AFP photographer in the area said floodwaters remained stubbornly high earlier Monday, with many people making their way to safety in rafts cobbled together from old tyres, salvaged wood and large plastic bottles.

The United Nations said swollen rivers threaten more areas of the country, adding it could be days before the true extent of the disaster emerges.

"Logistics are extremely difficult. Assessment teams are having a hard time reaching affected areas," said Pierre Peron, Myanmar spokesman for the United Nations Office for the Coordination of Humanitarian Affairs.

Myanmar's previous junta government was accused of callous indifference in its sluggish response to Cyclone Nargis in May 2008, which left nearly 140,000 people dead or missing.

But the current quasi-civilian government has seemed eager to show it is mobilising.

President Thein Sein promised authorities would do their "utmost" to provide relief, according to the state-run Global New Light of Myanmar.

Landslides in Chin state -- south of Sagaing -- have destroyed 700 homes in the state capital Hakha, which is completely cut off from surrounding areas, the report added.

Rains have also battered the western state of Rakhine which already hosts about 140,000 displaced people, mainly Rohingya Muslims, who live in exposed coastal camps following deadly 2012 unrest between the minority group and Buddhists.

A consortium of 60 local aid groups meeting in Yangon Monday criticised the government response to the flooding.

"People are trapped, they have no way out," said Aung Myo Min, one of the coordination committee members, adding that government warnings had come "very late".

- Monsoon misery -

The annual monsoon is a lifeline for farmers across the region but heavy rains and powerful cyclones can also prove deadly.

Poor infrastructure and limited search and rescue capabilities routinely hamper relief efforts across the region, with roads, phone lines and electricity often knocked out by rising waters.

India, which receives nearly 80 percent of its annual rainfall from June to September, sees tragedy strike every monsoon season.

This year West Bengal has been hit hard with 48 people killed, according to state management minister Javed Ahmad Khan.

"More than 1.8 million people in 5,600 villages have been affected by the flooding... nearly 1.1 million have been moved to camps," Khan told AFP.

Pakistan has seen 116 people die so far.

Ahmed Kamal, spokesman for Pakistan's National Disaster Management Agency, said more than 850,000 people had been affected by this year's floods.

Dozens have also perished in Nepal and Vietnam following floods and landslides.

In Vietnam toxic mudslides from flood-hit coal mines in the northern province of Quang Ninh, home to the UNESCO-listed Halong Bay tourist site, claimed the lives of two families and spewed coal into town centres.