Six hospitals in the Indian capital Delhi have completely run out of oxygen and doctors say other hospitals have just a few hours' worth of supply left. A number of people have died while waiting for oxygen, and more than 99% of all intensive care beds are full.
India is in the grips of a second wave of Covid infections and on Thursday recorded the highest one-day tally of new cases anywhere in the world. The country has recorded close to 16 million confirmed infections.
There have been 314,835 new coronavirus cases in the past 24 hours, while deaths rose by 2,104.
There have been reports of state authorities stopping oxygen tankers from travelling to other states, according to Delhi television station NDTV. Some facilities have been accused of hoarding their supplies.
Indian politician, Saurabh Bharadwaj, who is being treated in a Delhi hospital for Covid, posted a plea for help in Hindi on Twitter, saying there were just three hours of oxygen left where he was.
"A lot of people are dependent on oxygen and without oxygen, these people will die just like fish die in the absence of water," he said. "This is a time for all to come together to work."
Families are also waiting hours to perform funeral rites, Reuters news agency reports, with at least one Delhi crematorium resorting to building pyres in its car park in order to cope with the numbers arriving. Crematoriums are holding mass cremations, and working day and night in several cities.
"During the first phase of coronavirus, the average here was eight to 10, one day it reached 18. But today the situation is very bad. Last night we cremated 78 bodies," Jitender Singh Shunty, who runs a crematorium in northeast Delhi, said.
"It is four times more frightful, this coronavirus... Many bodies are around, waiting. We have no place left in the crematorium to cremate them. Very bad times, very bad times," he added.
A doctor working in a government hospital in the south of India, who wished to remain anonymous, said tensions were running high.
"Patients are trying to hit doctors," they told the BBC. "They are blaming doctors for everything and even the [hospital] management is also blaming the doctors. It's a stressful environment."
"We have presently almost used 99% of oxygen ports - only 1% is left. It's a very pathetic situation."
India has seen a rapid rise in case numbers over the past month driven by lax safety protocols, a Hindu festival attended by millions and variants of the virus, including a "double mutant" strain.
Political parties have come under criticism for holding huge state election rallies - including one by Prime Minister Narendra Modi - in West Bengal. The government has defended the decision to continue with polling, which is taking place in phases, but India's election body has now banned campaign rallies.
Prime Minister Modi chaired a high-level meeting on Thursday to discuss the oxygen supply issue. According to a government statement, he was told that an "elaborate exercise" is under way, with state governments to identify their needs so they can be supplied with oxygen.
To transport oxygen around the country faster, the canisters are being airlifted and put on direct trains, the statement says. There is no national lockdown currently in place, and regions are implementing their own rules.
Delhi announced a week-long lockdown at the weekend, leaving just government offices and essential services like hospitals, pharmacies and grocers open.
Tougher restrictions have been announced in the worst affected state of Maharashtra, which is India's richest region and home to its financial hub, Mumbai. It has also been a Covid hotspot since the start of the pandemic, accounting for a quarter of India's cases.
Despite a promising start in January, India's inoculation drive has been lagging. Some 130 million doses have so far been administered, but with a population of more than a billion people, it is a small percentage, and the drive has been restricted to health workers, frontline staff, those above the age of 45 and anyone with co-morbidities.
Experts say India is unlikely to meet its target of covering 250 million people by July. From May 1, people above 18 will also be eligible for the vaccine. But there is a shortage of doses, which could slow it down further.
