Indians crowded grocery stores and pharmacies on Wednesday in a struggle for essential items after Prime Minister Narendra Modi ordered a total lockdown for three weeks to fight the coronavirus spread, one of the toughest such measures worldwide.India's tally of 536 cases and 10 deaths is dwarfed by China, Italy and Spain, but Modi and health experts have warned that the nation of 1.3 billion people faces a tidal wave of infections if harsh steps are not taken.People in the key cities of New Delhi, Mumbai and Bengaluru rushed to stock up after Modi decreed the shutdown in a speech televised nationwide, barely four hours before it took effect. Everything, except for essential services like supermarkets, is shut. Long queuesAs states shut their borders, long queues of trucks carrying milk, fruits and vegetables snaked down highways, even though Modi said essential services would be maintained countrywide.By converging around shops, you are risking the spread of COVID-19.No panic buying please.Please stay indoors. I repeat- Centre and State Governments will ensure all essentials are available. https://t.co/bX00az1h7l— Narendra Modi (@narendramodi) March 24, 2020"There are no clear instructions, police are telling us to close down the shop," said Ram Agarwal, a grocer in New Delhi swamped by people looking to buy dry food supplies and milk."Delhi Chief Minister Arvind Kejriwal in a news conference said that people crowding to buy essential commodities defeated the purpose of the lockdown," she said.Normally bustling railway stations in New Delhi were deserted. "Delhi looks like a ghost town," said Nishank Gupta, a lawyer. "I have never seen the city so quiet before."The government said on Wednesday that it is banning the export of hydroxychloroquine and formulations made from the medication, as experts test the efficacy of the drug in helping treat patients infected with Covid-19.TestingHydroxychloroquine, a malaria drug, is among the medications that are being tested, as a potential treatment for patients with the disease.India has already banned the export of all ventilators and sanitisers and personal protective equipment such as masks and clothing to contain the outbreak.Disruptions to online services added to people's woes. Walmart Inc's Flipkart has suspended services, the Indian e-commerce firm said in a notice on its website as the lockdown began. Amazon India's pantry service, which delivers groceries, was also not available in several cities.Anthony Thomas, a worker at a small online milk delivery service, who normally distributes 150 litres of milk and groceries in New Delhi each morning, said his employer had told him to stay home."There is no information yet on tomorrow's supplies," he added.