Prime Minister Narendra Modi has banned citizens from leaving their homes completely in light of the increase. Images and videos show chaotic scenes as people rushed to shops for supplies immediately after the announcement.
Prime Minister Modi said: “The entire country will be in lockdown, total lockdown.”
He added: “To save India, to save its every citizen, you, your family… every street, every neighbourhood is being put under lockdown.”
Mr Modi warned if India does not “handle these 21 days well, then our country… will go backwards by 21 years.”
He called on Indians to unite and take responsibility for tackling COVID-19.
Schools and universities will remain shut and almost all public gatherings will be banned.
Big cities such as Delhi and Mumbai were already under social distancing restrictions, but now the rules extend to the whole country.
Air and train travel has also been heavily restricted, with all international flights grounded.
The Foreign and Commonwealth Office has advised against all travel to the region and urged any Brits in India to make arrangements to travel back to the UK.
India has one of the highest populations in the world, standing at 1.3 billion.
Major concerns have been raised about how the country’s health system will be able to cope with the demand coronavirus could bring.
The prime minister has introduced extra funding to help the system cope, although for such a densely packed population it is feared the virus will spread exceptionally quickly.
Health researchers have warned more than a million people in India could be infected with the coronavirus by mid-May.
The Global Health Security index, and joint project developed by the Nuclear Threat Initiative (NTI) and the Johns Hopkins Center for Health Security, ranks India 57th out of 195 nations in terms of its pandemic preparation.
The 21 day period, or three weeks, is the recommended time it takes to break the cycle of infection.
The UK is just at the beginning of its initial three-week lockdown.