Indian capital New Delhi will stay in lockdown for another week because of the surge in Covid cases, the megacity's chief minister said on Saturday.

"Lockdown in Delhi is being extended by one week," Arvind Kejriwal said on Twitter. 

The current shutdown had been due to expire on Monday but the number of cases is still rising fast in the city of 20 million people.

According to health ministry data released on Saturday, New Delhi recorded 27,000 new cases and 375 deaths.

But with tests recording a positivity rate of almost 33 percent, experts suspect the real numbers are much higher.

The city's hospitals have been overwhelmed, with lethal shortages of beds, drugs and oxygen meaning many people have been dying outside without treatment.

Many of Delhi's graveyards are now full and many crematoriums are working around the clock and burning bodies in waste ground and car parks.

Nationally India reported more than 400,000 new cases on Saturday in the past 24 hours, the first country to do so. 

April saw the country report seven million new infections.

Fauci recommends India lockdown as cases surge

India should go into lockdown for several weeks to arrest the current devastating surge in Covid cases, top US pandemic advisor Anthony Fauci said in comments published Saturday.

Prime Minister Narendra Modi's government has resisted imposing a national lockdown after a nationwide shutdown a year ago caused widespread human suffering and a painful economic hit.

"I think the most important thing in the immediate is to get oxygen, get supplies, get medication, get PPE, those kinds of things," the Indian Express daily quoted Fauci as saying in an interview.

"But also, one of the immediate things to do is to essentially call a shutdown of the country," he said.

"And if you shut down, you don't have to shut down for six months. You can shut down temporarily to put an end to the cycle of transmission," he added.

"No one likes to lock down the country... But if you do it just for a few weeks, you could have a significant impact on the dynamics of the outbreak."

India recorded more than 400,000 new cases on Saturday and added more than seven million infections in April, overwhelming its health care system in many places.

Many states have imposed heavy restrictions on activity, particularly in the western state of Maharashtra and the capital New Delhi where hospitals are at breaking point.

The hard-hit capital extended its shutdown for another week on Saturday.