Japanese Prime Minister Shinzo Abe on Thursday expanded a state of emergency due to the coronavirus to cover the whole country to stem the growing spread of the disease.

The declaration allows regional governors to urge people to stay indoors, but with no punitive measures or legal force, the measure is far weaker than strict lockdowns seen in other parts of the world. Abe had already declared a month-long state of emergency in seven regions, including Tokyo, where a recent spike in cases has prompted warnings that emergency medical facilities could collapse.

"Areas where a state of emergency should be carried out will be expanded from the seven prefectures to all prefectures," Abe told a special meeting of medical experts called to discuss the disease.

He said the state of emergency would remain in force until May 6.

Since the initial emergency came into effect on April 8, several regional governors have called for the measures to be expanded to cover their areas -- warning of a growing number of coronavirus infections and overwhelmed medical facilities. Some have declared their own local emergencies, even though they carry no legal force.

Japan has so far seen a relatively small outbreak of the virus -- despite recording its first case in mid-January -- with around 8,500 infections and 136 deaths by Thursday. But local medical associations and experts have sounded the alarm, and Abe has asked people in areas already under a state of emergency to reduce contact with others to avoid an explosive growth in infections.

In Tokyo, the governor has called on people to work from home, and significant drops have been seen in the number of people commuting each day on the city's notoriously crowded transport system.

But while some central areas have been uncharacteristically deserted, local neighbourhoods have remained relatively bustling, raising concerns about whether the measures will be sufficient.

Japan's two emergency medical associations this week issued a joint statement warning they are "already sensing the collapse of the emergency medical system", with hospitals unable to deal with patients suffering from non-coronavirus ailments.

And in Japan's third-biggest city Osaka, the mayor has appealed for donations of raincoats to serve as personal protection for health workers who he said were being forced to resort to garbage bags.