NEW DELHI - Torrential monsoon rains swept away homes and triggered landslides across South Asia, affecting millions of people and claiming more than 100 lives, officials said on Tuesday.

The monsoon is crucial for irrigation and groundwater supplies in the impoverished region, home to a fifth of the world's population, and brings relief after the unforgiving summers.

But the downpours, which stretch from June to September, can turn deadly and have wreaked havoc again this year across India, Nepal and Bangladesh, with people, dwellings and boats in remote low-lying areas washed away.

At least five children drowned in Bangladesh on Monday, taking the toll in the country to 34, including 18 hit by lightning and seven who drowned after their boat capsized in choppy waters in the Bay of Bengal.

Hundreds of thousands have been marooned by floodwater in the country's north, with one of the major Himalayan rivers, the Brahmaputra, over a meter above the "danger level", officials said.

In Nepal, at least 67 people have died, although floodwaters have started to recede. Images showed rescuers using inflatable dinghies to evacuate families trapped in flooded houses.

At least 1,445 people have been rescued and evacuated to safer destinations, according to Nepal Police in a statement.

Health experts have warned of possible outbreaks of waterborne diseases and called for international help.

Nearly 50 people have been killed in India, with two eastern states - Assam and Bihar, which borders Nepal - bearing the brunt of the deluge.

About 4.3 million people have been displaced from their homes in Assam in the last 10 days due to rising waters across the mostly rural northeastern region, according to a government release on Monday.

Photos showed residents crammed in boats carrying their belongings to safer areas in Morigaon, one of the worst-affected districts. The roofs of their submerged homes were just above water.

So far, 11 people have died in the state and nearly 83,000 people displaced by flooding.

Authorities also scrambled to reach animals marooned by the deluge at the state's World Heritage listed Kaziranga National Park, which is home to two-thirds of the world's one-horned rhinos.

In Bihar, 24 deaths were reported, with 2.5 million residents affected.

Among the dead were three children who drowned after they went to check the rising water level in a canal. Two others died while playing near a ditch filled with floodwater, the Press Trust of India reported.

Television channels showed roads and railway lines in Bihar submerged, with people wading through chest-high, churning brown waters, carrying their belongings on their heads.

The United Nations said on Monday it "stands ready to work with the authorities in the affected countries as they respond to the humanitarian needs resulting from this ongoing monsoon season".

Agencies - Xinhua