NEW DELHI -- Indian Prime Minister Narendra Modi on Tuesday extended the country's three-week lockdown until May 3 to combat the spread of the coronavirus.

"We have to be very vigilant about hot spots," or clusters with positive cases, Modi said in a televised address. "The creation of new hot spots will further challenge our hard work and penance," he said, adding that stricter measures will be taken to fight the pandemic in the coming week.

Modi's address comes as India's tally of confirmed coronavirus cases reached 10,363, an increase of 1,211 since Monday morning and the biggest 24-hour spike so far. That number includes 339 deaths and 1,035 recoveries, according to the Ministry of Health and Family Welfare.

India's lockdown, that has asked its 1.3 billion people to stay at home, is the largest in the world. Modi said every town and district will be evaluated based on how closely the lockdown is being adhered to. Areas that make the grade, and are not classified as hot spots, may be allowed to begin "some necessary activities," starting April 20. "However, this permission will be conditional, and the rules for going out will be very strict. Permission will be withdrawn immediately if lockdown rules are broken," he warned.

Modi earlier announced an initial three-week lockdown, which began March 25. Since then people have remained indoors, with only essential services such as hospitals, police and fire departments, and grocery stores remaining open. All public transport is suspended.

In late March, tens of thousands of migrant laborers began leaving cities on foot for their home towns and villages, some hundreds of kilometers away, after economic activity ground to a halt and public transport was halted. The exodus prompted the government to set up shelters and provide food and monetary assistance to migrants.

According to estimates by the Centre for Monitoring Indian Economy (CMIE), a private think tank, the unemployment rate jumped to 23.4% in the week ended April 5, compared with 8.7% for the whole of March. Auto sales in March plunged by 61% on the year to 156,041 vehicles, including cars and trucks, the Society of Indian Automobile Manufacturers said Monday. The lockdown's extension is expected to hit April's results even harder, as Japanese automaker Suzuki Motor decided to prolong its suspension of plant operations in India following the government's announcement.

"From an economy-only point of view, [the lockdown] undoubtedly looks costly right now. But measured against the lives of Indian citizens, there is no comparison," Modi said in his Tuesday address, adding, "We have to ensure that coronavirus is not spread around the country, at any cost."

The Federation of Indian Chambers of Commerce and Industry said in response to the speech that it is encouraged by Modi's decision to prioritize saving lives, while taking measures to protect livelihoods and the economy.

"Estimates show that India may be losing around 400 billion rupees ($5.25 billion) daily due to the national lockdown, with an estimated loss amounting to 7 trillion to 8 trillion rupees during the past 21 days," Sangita Reddy, the organization's president, said in a statement. "It is also expected that close to 40 million jobs are at risk during the period [from] April to September 2020. Hence an urgent relief package is also critical."

Capital Economics, a research specialist, said: "With many households having no savings buffers, and large parts of the economy remaining closed, the Finance Ministry now needs to urgently step up its response to prevent turning the public health crisis into a humanitarian and banking crisis."

"Our working assumption has been that some form of widespread shutdown will remain in place for three months," it said in a note. "With large parts of the manufacturing, construction, transport, retail, leisure and recreation sectors remaining inactive for an extended period, we think the economy will grow by just 1% [in 2020], the weakest pace of annual growth in four decades."

Modi defended his government's response to the outbreak, saying India began screening travelers from coronavirus-affected countries at airports long before it had a single case of its own, and required a 14-day quarantine for those coming from abroad before India had 100 confirmed cases.

India, which reported its first coronavirus cases in late January, had only 550 confirmed infections when it took the "big step" of imposing a complete 21-day lockdown, he said. "India did not wait for the problem to [become] aggravated. Rather, we attempted to nip the problem in the bud by taking quick decisions as soon as it arose."

Modi assured people that India has ample reserves of medicine, food and other essential goods, and that supply-chain constraints are being removed. "We are making rapid progress in ramping up health infrastructure as well. From having only one testing lab for coronavirus in January, we now have more than 220 functional testing labs," he said.

He also urged the country's young scientists" to come forward and take the lead in creating a vaccine for coronavirus for the welfare of the world, for the welfare of the human race."

Modi asked people to take special care of elderly people in their homes, and to take social distancing measures, including wearing homemade masks. He also said they should download the government's Aarogya Setu mobile app to track infections in their area.He urged people make sure that those in poverty have enough food and told employers not to fire those "who work with you in your business or industry." Modi said India's "corona warriors" -- doctors, nurses, sanitation workers and the police -- deserved the utmost respect.