More than 60 million people in India — 10 times the official figure — could have contracted the novel coronavirus, the country's lead pandemic agency has said, citing a nationwide study measuring antibodies.

According to official data India, home to 1.3 billion people, is the world's second most infected nation, with more than 6.1m cases, just behind the United States.

But the real figure could be much higher, according to the latest serological survey — a study testing blood for certain antibodies to estimate the proportion of a population that has fought off the virus.

"The main conclusions from this sero-survey are that one in 15 individuals aged more than 10 have been exposed to SARS-CoV-2 by August," Indian Council of Medical Research (ICMR) director-general Balram Bhargava said at a health ministry press conference.