India's total COVID-19 cases have passed 18 million after another world record daily infection and death tally and as the government rejected reports of problems with its vaccine campaign.
India reported 379,257 new COVID-19 cases and 3,645 new deaths on Thursday, according to health ministry data. It was the deadliest day so far for any country hit by the pandemic.
India's best hope to curb its second deadly wave of COVID-19 was to vaccinate its vast population, said experts, and on Wednesday it opened registrations for everyone above the age of 18 to be given jabs from Saturday.
But the country, which is one of the world's biggest producers of vaccines, does not have the stocks for the estimated 600 million people becoming eligible.
Many people who tried to sign up complained on social media that they could not get a slot or simply could not get online to register as the website repeatedly crashed.
"Statistics indicate that far from crashing or performing slowly, the system is performing without any glitches," the government said in a statement late on Wednesday.
The government said more than 8 million people had registered for the vaccinations, but it was not immediately clear how many had got slots.
About 9 per cent of India's population have received one dose since the vaccination campaign began in January with healthworkers and then the elderly.
The second wave of infections has overwhelmed hospitals and crematoriums and prompted an increasingly urgent response from allies overseas sending equipment.
"India's COVID outbreak is a humanitarian crisis," US Democratic Senator Elizabeth Warren said on Twitter.
She said she was writing to the main vaccine manufacturers to find out what steps they're taking to expand global access to their vaccines to save lives and prevent variants from spreading around the world.
Two planes from Russia, carrying 20 oxygen concentrators, 75 ventilators, 150 bedside monitors, and medicines totalling 22 metric tonnes, arrived in the capital Delhi on Thursday.
The United States is sending supplies worth more than $100 million to India, including 1,000 oxygen cylinders, 15 million N95 masks and 1 million rapid diagnostic tests, the White House said in a statement on Wednesday. It said the supplies will begin arriving on Thursday.
The United States also has redirected its own order of AstraZeneca manufacturing supplies to India, which will allow it to make over 20 million doses of COVID-19 vaccine, according to the White House.
India will receive a first batch of Russia's Sputnik V vaccine against COVID-19 on May 1. Russia's RDIF sovereign wealth fund, which is marketing Sputnik V globally, has already signed agreements with five leading Indian manufacturers for over 850 million doses of the vaccine a year.
Delhi is reporting one death from COVID-19 every four minutes and ambulances have been taking the bodies of COVID-19 victims to makeshift crematorium facilities in parks and parking lots, where bodies were burned on rows and rows of funeral pyres.
Prime Minister Narendra Modi has been criticised for allowing massive political rallies and religious festivals which have been super spreader events in recent weeks.
More than 8.4 million eligible voters are set to vote on Thursday in the last phase of an eight-part election in the eastern Indian state of West Bengal, even as the state witnesses a record rise in coronavirus cases.
The South Asia head of the International Federation of Red Cross and Red Crescent Societies, Udaya Regmi, said the world was entering a critical phase of the pandemic and needed to have vaccinations available for all adults as soon as possible.
Early modelling showed that the B.1.617 variant of the virus detected in India had a higher growth rate than other variants in the country, suggesting increased transmissibility, it said.
The World Health Organisation said in its weekly epidemiological update that India accounted for 38 per cent of the 5.7 million cases reported worldwide to it last week.