NEW DELHI - Prime Minister Narendra Modi announced a three-week countrywide lockdown, starting at midnight on Tuesday (March 24), even as he made a strong appeal to people to stay home in what is essentially the biggest lockdown in the world to curb the coronavirus pandemic.

The world's second most populous country, with 1.35 billion people, has hitherto reported over 500 Covid-19 cases, with 10 deaths.

"The next 21 days are crucial for us. It is most crucial to break the cycle of infection. If we are not able to manage this pandemic in the next 21 days, the country and your family will be set back by 21 years," said Mr Modi on Tuesday in his second address to the nation on the crisis.

"If we are not able to manage the next 21 days, then many families will be destroyed," he added.

Mr Modi also highlighted how advanced economies with strong health infrastructure like the United States and Italy were struggling to cope with Covid-19.

"The ray of hope comes from those countries which have been able to control coronavirus to an extent... for weeks people from these countries did not leave their homes."

He accepted the lockdown would come at an economic cost, while announcing 150 billion rupees (S$2.88 billion) for testing facilities, personal protective gear, ICU beds and other essential equipment.

The government will punish those who flout the lockdown under the National Disaster Management Act, which details punishment of up to two years in jail.

The government has taken several stringent measures leading up to the announcement of a complete lockdown. These range from stopping international flights to grounding domestic flights and train services.

Even before his announcement, most of India had come under lockdown, with 32 Indian states shutting all offices and shops except essential services and people being asked to stay at home.

The government on Tuesday banned the export of ventilators, other ICU equipment and sanitisers.

The nationwide lockdown, which is expected to be strongly implemented, found support across the country amid rising concern as reports told of sharply rising infection rates in other countries.

"We are now at a collective turning point, where we must stop, listen & and help the government implement the 21-day, all-India lockdown. The time of great fear requires solidarity, humanity, sacrifice & hope. Not hysteria & rumour mongering. #21daysLockdown,'' tweeted filmmaker Mahesh Bhatt.

Essential services, including groceries, pharmacies and medical services will be available during the lockdown period, with local authorities asked to facilitate home deliveries.

But people were rushing to grocery shops to stock up on essentials on Tuesday even before Mr Modi's address, with reports of panic buying after his address.

On Tuesday, north-east India reported its first case. The state of Manipur reported that a woman with a history of travel to the UK had tested positive.

World Health Organisation executive director Michael J Ryan noted that India had experience in eradicating pandemics, mainly small pox and polio.

"There is a need in the number of labs where a surge is seen...India led the world in eradicating two pandemics, small pox and polio so India has a tremendous capacity," Mr Ryan said at a press conference.

"There are no easy answers. It is exceptionally important that countries like India show the way to the world as they have done before."