India accounted for nearly half the coronavirus cases reported worldwide last week and a quarter of the deaths.
Neighbouring countries are also seeing cases rising, as they attempt to ramp up vaccination programs which only started in the last couple of months.
Sri Lanka on Thursday became the latest of India's neighbours to seal its borders with the South Asian giant as it battles a record coronavirus surge.
Bangladesh and Nepal have also banned flights and sought to close their borders with India, where a huge rise in numbers in the past three weeks has taken deaths past 230,000 and cases over 21 million.
All three countries are fighting their own pandemic surges, which Red Cross leaders have described as a “human catastrophe.”
Unicef warned of “real possibility” that the health system in South Asia will be strained to a breaking point as the deadly new surge in Covid-19 cases are unlike anything the region has seen before.
Hopes that India's deadly second wave of Covid-19 was about to peak were swept away on Thursday as it posted record daily infections and deaths and as the virus spread from cities to villages across the world's second-most populous nation.
India reported a record 412,262 new cases and a record 3,980 deaths. Infections have now surged past 21 million, with a total death toll of 230,168, according to government data.
Experts, however, say India's actual figures could be five to 10 times the official tallies.
The country's top scientific adviser has warned of a possible third wave of infections.
What's happening elsewhere in the region?
According to the International Red Cross, South Asian countries are being overwhelmed by a surge of infections as India’s outbreak is spreading across the region.
After going through a second wave in October last year, Pakistan is witnessing a third surge with infections picking up sharply throughout March.
It has imposed new restrictions in areas with rising cases, making masks mandatory and limiting public gatherings.
In Nepal, there are fears of a second wave as infections began to show an increase in late March.
Afghanistan has also reported a rise in new cases at the start of April, but there are questions about the reliability of its official figures.
In Sri Lanka, daily cases are going up but not at the rate of its neighbours.
What data says?
In all the neighbouring countries of India, except Bhutan, the infection is increasing by leaps and bounds. In some of these countries, 35% to 45% of the tests have returned positive.
Amid the situation, the International Federation of Red Cross and Red Crescent Societies (IFRC) have called on the world to stand by the people of the region.
"We need to act now and we need to act fast to have any hope of containing this human catastrophe," said IFRC Asia-Pacific director Alexander Matheou.
Although not as bad as India, the situation in Nepal, Sri Lanka, Maldives, Myanmar and Afghanistan is deteriorating.
Within a week, Sri Lanka saw its new infection rate go up by a stagerring 101% while Covid 19 deaths rose by more than 80%.
In Nepal, the number of people infected has increased by 112% and the number of deaths has increased by 142%.
In the Maldives, infections rose by 74%, but the death toll went up by 300%.
In Myanmar, the infection rate has risen by 23% with deaths increasing by 100%.
Infection and death rates have also increased in Afghanistan.
Nepal
Nepal is being overwhelmed by a surge of infections as India's outbreak spreads across South Asia, the International Federation of Red Cross and Red Crescent Societies said.
With 57 times as many cases as a month ago, Nepal is seeing 44% of tests come back positive, it added.
Towns near the border with India are unable to cope with the growing numbers seeking treatment, while just 1% of its population was fully vaccinated.
Nepal suspended international flights a week ago, until May 14.
Just two return flights a week are allowed to India, to bring back stranded nationals. Most border crossings are also closed and only returning Nepalis can use those still open.
Many hospitals in Nepal are overflowing with Covid-19 patients, according to the IFRC.
“Southern towns near the Indian border are unable to cope with the growing number of people needing medical treatment,” it said.
Sri Lanka
Sri Lanka on Thursday became the latest of India's neighbours to seal its borders with the South Asian giant as it battles a record coronavirus surge.
The Sri Lankan government banned flight passengers from entering India, as the country reported its highest daily toll of 14 deaths and 1,939 infections in 24 hours.
Sri Lanka's navy said it had stepped up patrols to keep away Indian trawlers, adding that on Tuesday it stopped 11 such vessels which had crossed the narrow strip of sea dividing the two neighbours.
India is the largest tourist market for Sri Lanka and the Maldives, both of which now face huge losses from the fast-spreading Covid-19 new wave.
Sri Lanka has reported 117,529 infections with 734 deaths since the start of the pandemic.
Maldives
Maldives began a night-time curfew from Thursday to control a doubling of daily coronavirus infections that was fuelled by crowds at a local election and family gatherings during the ongoing Muslim fasting month of Ramadan.
The Health Protection Agency announced the curfew on Wednesday after government data showed daily cases grew to 734 from 318 a week ago. Most of the cases reported on Wednesday were in the crowded capital Male.
Restrictions have been placed on movement between islands, although there are no curbs on tourists headed to private island resorts if they can produce a negative Covid-19 test. The health agency also ordered mandatory physical distancing in mosques.