India's coronavirus death toll has passed 250,000 as the World Health Organization said the variant fuelling the surge had been found in dozens of countries across the globe.

While vaccinations have helped to ease the pandemic crisis in the United States and Europe, India is in the grip of a devastating wave.

Another 4,205 deaths were today confirmed over the previous 24 hours, a national record, taking total fatalities to 254,197.

But many experts believe the official numbers of people dying in India, which has one of the world's most poorly funded health care systems, are an underestimate.

"Even three to four times would be an underestimate," Anant Bhan, an independent health policy and bioethics researcher, told AFP.

Across India overwhelmed hospitals have been unable to treat people and there have too many bodies for crematoriums to deal with, and many Covid-19 deaths are not properly recorded as such.

Bodies being burnt in car parks and other public places have highlighted the scale of the crisis.

Bodies have also been seen floating down the holy Ganges river, stoking concerns that the virus is now raging in India's vast rural hinterland where two-thirds of people live and where health care is patchy.

Today, the number of bodies of suspected virus victims washing up on the banks of the Ganges in the northern state of Bihar rose to 71, according to officials.

Bihar's water resources minister said a net had been placed in the river to catch any more bodies.

Huge political rallies and religious events that attracted millions of people over recent months are two key factors being blamed for India's crisis.

A variant of the virus called B1617, which was first detected in India in October, is another.

Many nations have shut their borders to travellers from India in a bid to stop the variant from reaching their shores.

But it has been detected in at least 44 nations, the World Health Organization said yesterday.

Britain had the largest number of Covid-19 cases caused by the variant outside India, according to the WHO.

The organisation this week declared the strain a "variant of concern", placing it alongside three others that were first detected in Britain, Brazil and South Africa.

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Japan's coronavirus vaccine booking system crashes

Technical problems derailed Japan's coronavirus vaccination booking system today, compounding frustration over the government's handling of new outbreaks of infections and an inoculation drive that critics say has been woefully slow.

The online system to book a vaccine crashed in many places including parts of Tokyo and the western city of Minoh because of a global problem with US cloud computing vendor Inc, public broadcaster NHK reported.

Salesforce's chief technology officer said on Twitter that the company was experiencing a "major disruption", later updating to say services had been mostly restored.

A representative of the health ministry's vaccine office was not immediately available when contacted by Reuters.

The ministry has faced numerous technical problems throughout the pandemic, from a contact tracing application that failed to pass on vital information to a cumbersome database that health workers were reluctant to use.

Japan has only inoculated 2.8% of its population, the lowest rate among wealthy countries despite an ambitious government target of giving shots to its 36 million elderly people by July, when the Olympics Games are due to open in Tokyo.

The campaign was initially slow because of tight supplies of imported doses of the Pfizer vaccine but has since been plagued by a shortage of manpower and other logistical snags.

Brazil to start vaccinating Olympic athletes

Brazil will begin vaccinating Olympic athletes and other members of its Tokyo-bound delegation against Covid-19 from today, officials said.

The hard-hit South American country is struggling to secure enough vaccines for its 212 million people, but will be able to immunise its Olympians thanks to donated doses from pharmaceutical companies, health officials said.

Health Minister Marcelo Queiroga told a news conference that 1,814 members of the delegation would be vaccinated starting today, including Olympic and Paralympic athletes, coaches, staff members and journalists traveling to the Games.

"The doses will be donated by pharmaceutical companies so that (the program) will not affect our national immunisation campaign," he said.

Pfizer is expected to donate 4,050 doses of its vaccine and Chinese lab Sinovac 8,000, officials said.

The extra doses - more than 8,000 - will be donated to the national campaign, they said.

Covid-19 has claimed more than 425,000 lives in Brazil, second only to the US.

The country has struggled to secure enough vaccines and has had to suspend immunisation campaigns at times in various cities.

Members of the Olympic delegation will have until 21 June to get both vaccine doses, officials said - two weeks before the team flies to Japan.

Delayed by a year because of the pandemic, the Games are scheduled to be held from 23 July to 8 August.

Other countries have recently announced Olympians will be given priority status for vaccination, including Australia, which began administering them shots on Monday.