India's capital New Delhi will impose a week-long lockdown from Monday night, officials said, as the megacity struggles to contain a huge surge in Covid-19 cases with hospitals running out of beds and oxygen supplies low.

The vast nation of 1.3 billion people reported a record high of 273,810 infections on Monday -- the fifth consecutive day of more than 200,000 cases.

In Delhi -- the worst-hit city in India -- 25,500 fresh cases were reported on Sunday, with almost one-third of those tested returning positive coronavirus results.

"Delhi's health system is at a tipping point. The Covid-19 situation is pretty critical," Delhi Chief Minister Arvind Kejriwal said in a televised address.

"If we don't impose a lockdown now, we will be looking at a bigger disaster. From tonight there will be a lockdown until next Monday."

Kejriwal said businesses would be shut and movement around the northern city of 20 million limited to essential services.

"The lockdown doesn't end the pandemic but just slows it. We will use this week-long lockdown to improve our healthcare," he said, adding that the healthcare system was "under severe strain" and had "reached its limit".

The restrictions followed similar measures in other parts of India, including in the western state of Maharashtra, home to financial capital Mumbai, and the southern state of Tamil Nadu.

Social media has been flooded with pleas by desperate families for hospital beds, oxygen supplies and drugs.