“Looking at the trend, I am worried that unless we take further steps, things will gradually get worse, or another big cluster may push things over the edge,” Lee said, describing the new measures as a “circuit breaker”.

“It will help reduce the risk of a big outbreak occurring and it should also help to gradually bring our numbers down,” he said in a national address, his third since the Covid-19 outbreak.

Lee said more support for households and businesses was on the way, “over and above what was provided in the two earlier budgets”. The new stimulus measures will be announced by Deputy Prime Minister Heng Swee Keat in parliament on Monday.

Singapore will also no longer discourage people from wearing face masks, Lee said. This is a reversal of the city state’s earlier advice that masks should only be used when a person is sick and on his or her way to seek medical attention. The policy change comes from evidence that an infected person can show no symptoms but still pass on the virus to others.

Lee said the government would distribute reusable masks to all households from April 5, while conserving surgical masks for health care workers. Singapore had previously distributed four masks to each household but told residents to only use them if sick.

With Friday’s announcement, Singapore joins its neighbours in the region in restricting the movement of residents. Malaysia is under a partial lockdown, Thailand has put in place an evening curfew while Hong Kong has kept schools closed since the Lunar New Year break in February.

Singapore has kept schools open, but this week began keeping pupils at home one day a week for online learning.

Coronavirus Singapore: 100 to 1,000 infections in one month. What happened?

While Singapore has won global praise for its stringent contact tracing and quarantine measures, locally transmitted infections spiked recently after a wave of residents returned from virus-stricken countries, such as the United States and Britain.

Pointing to the rise in local cases, Lee said that “despite our good contact tracing, for nearly half of these cases, we do not know where or from whom the person caught the virus”.

“This suggests that there are more people out there who are infected, but who have not been identified. And they may be passing the virus unknowingly to others.”

Lee urged Singaporeans to do three things: stay home as much as possible, avoid socialising with people outside of their households, and only go out for essential things.

“If we don’t go out, if we avoid contact with others, then the virus won’t be able to spread. It is as simple as that,” he said.

Bars and entertainment venues in the island nation have been closed since March 27, with the authorities introducing penalties for individuals and businesses if they did not ensure that people remained up to a metre apart at restaurants.

Those flouting the measures would face a fine of up to S$10,000 and/or six months in jail.

Coronavirus: Singapore mulls punishing companies for not following social distancing, telecommuting rules

Singapore on March 26 released a second stimulus package of around S$48 billion (US$33.7 billion) to deal with the pandemic’s economic fallout, with the government tapping its vast reserves for only the second time in history to mitigate what is likely to be a deep recession.

A key part of the stimulus package involves ramping up a jobs support scheme first announced in February. The government will now offset up to 25 per cent of the first S$4,600 of workers’ monthly wages for a nine-month period. That is higher than the 8 per cent quantum and S$3,600 cap announced in February.