A top scientific adviser to the Indian government warned on Wednesday the country would inevitably face further waves of the coronavirus pandemic, as almost 4,000 people died in the space of a day.

With hospitals scrabbling for beds and oxygen in response to a deadly second surge in infections, the World Health Organization said in a weekly report that India accounted for nearly half the coronavirus cases reported worldwide last week and a quarter of the deaths.

Many people have died in ambulances and car parks waiting for a bed or oxygen, while morgues and crematoriums struggle to deal with a seemingly unstoppable flow of bodies.

The government's principal scientific adviser, K. VijayRaghavan, warned that even after infection rates subside the country should be ready for a third wave.

"Phase 3 is inevitable, given the high levels of circulating virus," he told a news briefing. "But it is not clear on what timescale this phase 3 will occur... We should prepare for new waves."

Prime Minister Narendra Modi's government has been widely criticised for not acting sooner to suppress the second wave, after religious festivals and political rallies drew tens of thousands of people in recent weeks and became "super spreader" events.

"We are running out of air. We are dying," the Booker Prize-winning author Arundhati Roy wrote in an opinion piece that called for Modi to step down.

"This is a crisis of your making," she added in the article published on Tuesday. "You cannot solve it. You can only make it worse....So please go."

India's delegation to the Group of Seven foreign ministers' meeting in London is self-isolating after two of its members tested positive for COVID-19, Britain said on Wednesday

Foreign Minister Subrahmanyam Jaishankar, who is in London, said in a Twitter message that he would attend virtually.

GOVERNMENT RESISTING LOCKDOWN

Deaths rose by a record 3,780 during the past 24 hours, health ministry data showed, and daily infections rose by 382,315 on Wednesday. The number has been in excess of 300,000 every day for the past two weeks.

Medical experts say India's actual figures could be five to 10 times the official tallies. The country has added 10 million cases in just over four months, after taking more than 10 months to reach its first 10 million.

The opposition has urged a nationwide lockdown, but the government is reluctant to impose one for fear of the economic fallout, although several states have adopted social curbs.

In the latest move the eastern state of West Bengal, where voters dealt Modi's party a defeat in an election last week, suspended local train services and limited working hours for banks and jewellery shops, among its steps to limit infections.

The central bank asked banks on Wednesday to allow more time for some borrowers to repay loans, as the crisis threatens a nascent economic revival.

FALL IN VACCINATIONS, TESTING

The surge in infections has coincided with a dramatic drop in vaccinations because of supply and delivery problems, despite India being a major vaccine producer.

At least three states, including Maharashtra, home to the commercial capital of Mumbai, have reported a scarcity of vaccines, shutting down some inoculation centres.

Lengthy queues formed outside two centres in the western city that still have vaccine supplies, and some of those waiting pleaded for police to open their gates earlier.

The government said production capacity for the antiviral drug remdesivir, used to treat COVID-19 patients, has trebled to 10.3 million vials per month, up from 3.8 million vials a month ago.

But daily testing has fallen sharply to 1.5 million, state-run Indian Council of Medical Research said, off a peak of 1.95 million on Saturday.

OUTBREAK SPREADING

Two "oxygen express" trains carrying liquid oxygen arrived in the capital, New Delhi, on Wednesday, railways minister Piyush Goyal said on Twitter. More than 25 trains have distributed oxygen supplies nationwide.

The government says supplies are sufficient but transport woes have hindered distribution.

Meanwhile, the outbreak continues to spread.

In the remote state of Mizoram bordering Myanmar, beds in its biggest coronavirus hospital are in such short supply that all victims of other diseases have been asked to leave, said government official Dr Z R Thiamsanga.

Just three of a total 14 ventilators were still available.

"In my opinion, a complete lockdown is required to control the situation," he told Reuters from the state capital, Aizawl.

Neighbouring Nepal is also 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.