A surge in recent days has seen patients' families taking to social media to beg for oxygen supplies and locations of available hospital beds, and has forced the capital New Delhi to extend a week-long lockdown.
The country of 1.3 billion has become the latest hotspot of a pandemic that has killed more than three million people, even as richer countries take steps towards normality with quickening inoculation programmes.
Irfan Salmani told AFP he had been going from hospital to hospital around Delhi for the past three days, searching for oxygen for his sister.
"I've never seen anything so terrible," he said. "I've been trying non-stop."
"What can I do?... I've just been facing rejection after rejection."
Read more: UK adds India to Covid travel 'red list' as PM cancels trip
France, Germany and Canada have also pledged support to India, which has driven increases in global case numbers in recent days, recording 352,991 new infections and 2,812 deaths on Monday - its highest tolls since the start of the pandemic.
Creaking health facilities in poorer countries were exposed Sunday when more than 80 people died as fire ripped through a Baghdad hospital for Covid-19 patients, sparking outrage and the suspension of top Iraqi officials.
Thailand enforced new restrictions Monday after a record daily death toll over the weekend, while the capital of neighbouring Cambodia has been under lockdown for 12 days as cases spike.
Vaccine surplus
The first of nine airline container-loads of supplies from the UK, including ventilators and oxygen concentrators, was set to arrive in India early Tuesday, Prime Minister Boris Johnson said, pledging the UK would do "all it can" to help.
The White House said it was making vaccine-production material, therapeutics, tests, ventilators and protective equipment immediately available to India.
But it did not mention whether it would send any of the 30 million AstraZeneca vaccine doses it currently holds in surplus, sparking accusations of hoarding.
India's Hindu-nationalist government is facing growing criticism for allowing mass gatherings across the country in recent weeks, with millions attending religious festivals and thronging political rallies.
The glitzy Indian Premier League is also under pressure, with a leading newspaper suspending coverage and slamming the IPL's decision to keep playing cricket as "commercialism gone crass".
The league suffered further blows Monday as Australians Adam Zampa and Kane Richardson became the latest players to leave after star India spinner Ravichandran Ashwin withdrew to support his family during the pandemic.
On Sunday, Twitter confirmed it withheld dozens of tweets -- including from opposition lawmakers - critical of the government's handling crisis after a legal demand from New Delhi.
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