Prime Minister Narendra Modi of India announced a sweeping, nationwide lockdown on Tuesday, declaring citizens across the country of 1.3 billion must stay at home for the next three weeks.

Addressing the country for the second time in a week, the prime minister said the decree, which takes effect at midnight Tuesday, was a necessary measure in battling an unprecedented health crisis.

“To save India and every Indian, there will be a total ban on venturing out of your homes,” Modi said in the televised address. “Every district, every lane, every village will be under lockdown.”

He added: “If you can’t handle these 21 days, this country will go back 21 years.”

In recent days, India has been taking more aggressive measures to curb the spread of coronavirus, introducing curfews in many states, banning international and domestic flights, and suspending passenger service across its extensive rail system.

The nationwide lockdown will affect nearly one-fifth of the planet’s population, amid growing concerns that the virus could spread unchecked through the world’s second-most populous nation. Through Monday, Indian health officials have reported 469 confirmed cases of coronavirus and 10 deaths, but have faced criticism for not testing more widely.

Essential services will remain open throughout the lockdown, including hospitals and pharmacies, while supermarkets, media, and certain other businesses are exempted from the stay-at-home order. Modi also pledged $2 billion to bolster the country’s struggling health care system.

After his televised address, the prime minister took to social media to reassure his 54 million followers, tweeting: “My fellow citizens, THERE IS ABSOLUTELY NO NEED TO PANIC. Essential commodities, medicines etc. would be available. Centre and various state governments will work in close coordination to ensure this. Together, we will fight COVID-19 and create a healthier India.”

He also urged citizens not to rush to stores and inadvertently aid the virus’s spread. “No panic buying please. Please stay indoors.”