JAKARTA - Indonesian health authorities have made it mandatory for citizens to wear face masks when venturing outside in a tough new measure to curb the spread of the coronavirus that has killed nearly 200 and infected almost 2,300 in the country.

The Health Ministry's director-general for disease control and prevention, Dr Achmad Yurianto, said everyone would have to wear masks in public with effect from Sunday (April 5), in line with a recommendation from the World Health Organisation (WHO).

"Surgical masks and N95 masks are only for medical workers. Please use cloth masks. This is important because we don't know if many people without symptoms are out there," he said at a daily press conference.

Indonesia reported 181 new coronavirus cases on Sunday, taking the total number of infections in the country to 2,273. There were another seven deaths over a 24-hour period, taking overall fatalities in the world's fourth-most populous nation to 198, the highest in South-east Asia. The number of recovered patients was up by 14 to 164.

"With this data, we believe that the transmission is still ongoing out there. There are still asymptomatic cases among us. Some of us still don't realise that we are vulnerable to infections," Dr Yurianto said of the latest figures.

Authorities have estimated that between 600,000 and 700,000 people in Indonesia are at risk of being infected by the virus. The government is expanding testing on a war-footing to curtail the outbreak.

President Joko Widodo declared a public health emergency on March 31.

The government also introduced large-scale social distancing measures that include the closure of schools and workplaces, the restriction of religious, social and cultural activities, activities in public places or facilities, and transport curbs.

Based on a ministerial regulation signed by Health Minister Terawan Agus Putranto last Friday, cities and regions can apply the large-scale social-distancing measures with the minister's approval whenever the number of infections and deaths rises significantly, and there is an epidemiological link with a similar incident in other areas or countries.

While the restrictions apply to many aspects of life, operation of essential services, such as supermarkets, pharmacies and gasoline stations, has been permitted.

Dr Pandu Riono, an epidemiologist at the University of Indonesia, estimated that with the current social-distancing measures being implemented, there would be between 1.25 million and 1.75 million infections in Indonesia, with 47,984 to 144,266 deaths. The outbreak is predicted to peak in late May or early June, he told The Straits Times.

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Speaking at the same press conference as Dr Yurianto, Health Ministry secretary-general Oscar Primadi said that the large-scale distancing measures sought to break the chain of infection. He said that quarantine measures would be enforced for suspected cases during the 14-day incubation period of the virus and would be extended should transmissions still occur.

"The indicator of success of the large-scale social distancing measures is the decline in the number of cases and absence of transmissions to new areas or regions," he said.

Public health experts and regional leaders had also called for the national government to ban the mass exodus from Indonesian cities, known as "mudik", for Eid ul-Fitri, over fear that millions of people from Jakarta, now the epicentre of the outbreak, would spread the disease to their hometowns across the archipelago.

Jakarta has so far been the area worst-hit by the epidemic, with the death toll in the city touching 95, with 1,124 infections.

Around half of the new infections announced on Sunday, 96, were in the city of more than 10 million dwellers.

However, President Joko resisted the demand, instead ordering local governments to monitor potential virus carriers.

The government is outlining rules that will enable public transport as well as private vehicles to implement social distancing measures during the exodus, Mr Ridwan Djamaluddin, deputy for infrastructure and transportation at the Coordinating Ministry for Maritime Affairs and Investment, said in a statement on Sunday.

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Public transport operators, for instance, are expected to raise ticket fees and restrict the number of passengers on journeys.

Economic incentives for those who opt not to return to their home towns are being prepared, Mr Ridwan added.

Meanwhile, the Philippine government said it was mulling over an extension of a lockdown on the main island of Luzon for two weeks. The current lockdown was set to expire on April 12. The country reported 152 new cases on Sunday, taking the number of infections on its soil to 3,246. There were also eight more deaths, taking the toll to 152.

Thailand reported 102 more confirmed cases of coronavirus infection on Sunday, taking the total number in the country to 2,169. The death toll increased by three to 23, with 46-year-old Thai man who had returned from Britain among the victims.