India’s population of more than 1.3 billion was asked to observe a “people’s curfew” on Sunday to try to halt the spread of coronavirus, an a lockdown of large swathes of the country has been announced for next week.

As cases of coronavirus in India rose to 390 and the death toll reached seven, usually hectic city streets were deserted and most businesses remained shut from 7am to 9pm to comply with the voluntary “janata curfew” that had been announced by the prime minister, Narendra Modi, last week.

“Janata curfew will end at 9pm but it doesn’t mean we should start celebrating,” Modi said on Sunday. “It’s the beginning of a long battle. People shouldn’t come out of houses in states which have announced a lockdown. In the rest of the states, if it is not very important, don’t come out of your houses.”

As the curfew began, there were announcements of longer-term measures including the suspension of India’s railway system, which in normal times carries 23 million passengers a day.

The capital, Delhi, which has reported six cases of coronavirus passed by local transmission, announced a draconian lockdown beginning at 6am on Monday.

People gather on a balcony to clap to thank essential service providers during a one-day curfew imposed to halt the spread of coronavirus Photograph: Diptendu Dutta/AFP via Getty Images

The city’s borders will be closed to all but food, water and fuel supplies, public transport will be shut, taxis and rickshaws will be kept off the roads and an order has been imposed preventing gatherings of more than four people. Homes of people instructed to go into quarantine have been marked with stickers in an effort to stop them going outside.

The number of coronavirus cases in India was up by 113 on Sunday, the steepest increase in a single day. The government had maintained that the cases were all connected to people who had travelled abroad, but the new cases in Delhi and an outbreak of the virus in a remote town in the state of Rajasthan indicate that the disease has begun to spread locally.

There are concerns that the low number of cases is due to a lack of substantial testing Photograph: Rafiq Maqbool/AP

While the number of confirmed cases to date seems low for a country of 1.3 billion people, there are concerns this is due to low levels of testing, with fewer than 20,000 people tested so far. In recent days the government has begun to ramp up its testing, expanding it to people in hospital with respiratory diseases such as pneumonia and to those coming back from abroad with symptoms.

Restrictions remained in place in all major cities, including Mumbai and Kolkata. The states of Rajasthan, Punjab and Jammu and Kashmir, and a total of 80 districts across India, have imposed full lockdowns involving the suspension of public transport and the closure of non-essential businesses.

In another move proposed by Modi, people across the country gathered at 5pm on their balconies and rooftops to clap and bang saucepans and crockery in a show of appreciation for the country’s healthcare workers.