Japan has so far reported a relatively low number of cases compared to its neighbours, including South Korea and China.
The prime minister, Shinzo Abe, told reporters on Saturday that the Japanese public should “brace for a prolonged battle against coronavirus”.
According to Japanese news agency NHK, Mr Abe said outbreaks in the US and Europe suggested the number of cases in Japan “could jump by more than 30 times in just two weeks”.
He stopped short of declaring a state of emergency, but promised the government would draw up an emergency economic stimulus package within the next ten days, including cash benefits for households.
On Friday, she reported 40 new cases and urged people to “share a sense of crisis and act responsibly” by avoiding non-essential outings.
She also urged people not to visit parks and other outdoor locations where cherry blossoms are coming into season, to help curb the spread of the disease, adding that the blossoms “will bloom again next year”.
Some experts have called into question Japan’s low figures and said the government had been complacent with testing.
Masahiro Kami, head of the Medical Governance Research Institute in Tokyo, told The Financial Times it did not make sense for a country next to China to be “seeing an expansion in cases only at the same time as European countries”.
He added it was “just a matter of testing”.
Back in February, newspaper The Japan Times reported hospitals in Japan were rejecting potential patients infected with coronavirus due to strict but vague testing guidelines.
Only people who had been in close contact with already confirmed cases, or those who recently travelled to infected areas in China, and had a fever and pneumonia-like symptoms were eligible for testing at the time.
Although the country was hit by an early wave of coronavirus in its initial spread from China, life in Japan has been relatively normal compared to numerous other countries trying to stop its spread.
Last weekend, 6,500 people gathered in the Saitama Stadium, north of Tokyo, to watch a popular kick-boxing event despite local authorities’ efforts to cancel the gathering.