India recorded more than 4,000 coronavirus deaths in a day for the first time and more states imposed lockdowns Saturday in a desperate bid to halt the devastating new surge.

The 4,187 new deaths took India's overall toll to 238,270 since the pandemic started. It added another 401,078 new cases in 24 hours taking its caseload to nearly 21.9 million -- second only to the United States.

Experts, who have expressed doubts about the official death toll, say the new wave may not hit a peak until the end of May and there have been mounting calls for tough nationwide measures.

Rahul Gandhi, leader of the opposition Congress party, called on Prime Minister Narendra Modi to order a national lockdown or the spread could be "devastating" for India and other countries.

Britain has already declared a new variant found in India to be of "concern".

The government, stung by criticism of its handling of the new crisis, has largely left individual state administrations to handle pandemic clampdowns.

While major cities such as New Delhi and Mumbai have been boosted by extra supplies of oxygen -- much of it from abroad -- and new hospital beds opened up, the southern states of Tamil Nadu, Karnataka and Kerala have all ordered lockdowns to counter an explosion in cases.

Karnataka, which includes the major IT hub of Bangalore, has ordered a statewide two-week lockdown from Monday in a bid to halt the spread of the virus.

The state added more than 48,000 cases in a day with Bangalore, home to many Indian and global information technology giants, bearing the brunt.

The city of nine million people, which saw 1,907 coronavirus deaths in April, has recorded more than 950 just in the first seven days of May.

A lack of oxygen and critical care beds is being blamed for the dramatic rise in the death rate.

Neighbouring Kerala, which is adding about 40,000 cases a day, started a nine-day lockdown from Saturday. Tamil Nadu, which includes the major city of Chennai, will start a 10-day lockdown from Monday.

Coronavirus is now spreading fast in India's rural areas
Coronavirus is now spreading fast in India's rural areas AFP / Prakash SINGH

Coronavirus cases and deaths have also shot up in West Bengal state since its election, which was marked by huge rallies organised by Modi and his arch-rival, state chief minister Mamata Banerjee.

The main city, Kolkata, also has a critical shortage of oxygen and beds.

The Hindu nationalist government imposed a three month nationwide lockdown last year which helped halt the spread of the first major wave, but also caused huge economic damage.

There are fears that the new surge could undermine the recovery in Asia's third biggest economy.

The growing death toll has added to pressure for the government to act however.

Gandhi said in his letter to the prime minister that "your government's lack of a clear and coherent Covid and vaccination strategy ... has placed India in a highly dangerous position."

Modi had "to understand India's responsibility in a globalised and interconnected world" as "home to one out of every six human beings on the planet."

"Allowing the uncontrollable spread of this virus in our country will be devastating, not only for our people, but for the rest of the world."

The government did not immediately respond.