India reported 58,097 cases on Wednesday, a six-fold rise in a week that experts say is fuelled by the Omicron variant.

Nearly a third of those infections came from Delhi and Mumbai.

Both cities have brought back curfews and other restrictions to halt the spread of the virus.

Dr NK Arora, head of India's vaccine task force, told NDTV on Monday that the third wave of the pandemic had already begun in the country, adding that the "whole wave seems to be driven by a new variant... Omicron".

The country has reported more than 2,000 Omicron cases - Maharashtra, of which Mumbai is the capital, is leading the tally (653), followed by Delhi (464).

Delhi's health minister Satyendar Jain has said that 81% of Covid samples in the city tested positive for Omicron.

The All India Institute of Medical Sciences (AIIMS) - one of India's major hospitals - in Delhi has cancelled winter leave for doctors, according to reports.

The rising infections are a sombre reminder of the devastating second wave India faced in April and May - daily averages of about 400,000 cases at the peak of the crisis.

The Centre on Wednesday confirmed the death of a man in Rajasthan as the first casualty due to the Omicron variant of coronavirus.

The samples of the 72-year-old man from Rajasthan's Udaipur, showed presence of the Omicron strain, joint secretary at Union health ministry Lav Agarwal said during a press conference in New Delhi.

"The government confirmed the death in Rajasthan has been counted as Omicron death in India. We can say this is the first death in India," Agarwal said.

As per government sources, the patient was diabetic for the past 17 years and it aggravated his situation. It was after his death that they found he was actually Omicron positive.

The man died in a Udaipur hospital on December 31.

Meanwhile, India’s Omicron tally on Wednesday rose to 2,135 cases. As many as 828 patients have recovered so far.