India's 1.3 billion people will go under "total lockdown" from midnight Tuesday for 21 days to combat the spread of the coronavirus pandemic, Prime Minister Narendra Modi said.
"From 12 midnight today, the entire country will be in lockdown, total lockdown," Mr Modi said in a national television address to the world's second most-populous nation.
"To save India, to save its every citizen, you, your family... every street, every neighbourhood is being put under lockdown."
Health researchers have warned that more than a million people in India could be infected with the coronavirus by mid-May, prompting the government to shut down all air and train travel, businesses and schools.
India has found 482 cases of the coronavirus and nine people have died from the Covid-19 disease it causes but alarm is growing across the region about prospects for its spread into impoverished communities and the ability of resource-starved public health sectors to cope.
Already health officials said the virus was spreading out of big Indian cities where it first appeared into the small towns that dot the landscape.
"India is today at such a stage, where our actions today will determine our ability to reduce the impact of this disaster," Mr Modi said, citing health officals and experts including the WHO for his dire warnings.
More than 377,300 people have been infected by the coronavirus globally and 16,520 have died since it emerged in China, according to a Reuters tally.
China's Wuhan where the virus emerged imposed a two-month lockdown which is only being eased.
"If these 21 days are not managed, the country and your family will go back 21 years... I am not saying this as your prime minister, I am saying it as your fellow citizen, family member."
The South Asian nation has already banned incoming international flights for a week from Sunday, and grounded domestic flights and shut sea and river ports.
Indian Railways - one of the world's biggest networks and carrying more than 20 million passengers daily - has cancelled all services except suburban and goods trains.
Police in India's northern city of Meerut are making citizens who break its lockdown hold up signs reading, "I am a friend of coronavirus," or "I am the enemy of society," before posting their pictures on Twitter.
Most of India, which had 482 infections and nine deaths by Tuesday, is under lockdown to curb the spread of the virus, including Meerut, in the most populous state of Uttar Pradesh.
Mosque worker Mohammad Alim, 40, said he took a widow and her three sons to a police station in the city on his motorbike on Monday night to report an altercation with neighbors.
"When I reached the police-station, the inspector handed me that shaming sign and clicked my picture," Alim told Reuters.
"I feel scared. I do not know who to complain to now," added Alim, who also accused officers of verbally abusing him.
Meerut police tweeted a picture of Alim holding a sign that read "I am a friend of coronavirus" with the caption, "Some people do not care about society's safety."