Japan's third-biggest city has appealed for donations of raincoats to be used as personal protection gear by hospital workers dealing with the coronavirus outbreak.

The shortage of proper protective clothing in Osaka is so acute that some health workers are resorting to wearing garbage bags over their scrubs.

"Please send us unused raincoats. Any colour will do," Mayor Ichiro Matsui told reporters on Tuesday.

The region is battling a growing number of cases, with more than 830 infections recorded -- the second-highest in the country after Tokyo's 2,171.

"Some hospital workers are wearing a garbage bag as an alternative to protective gear," Matsui said, adding the makeshift fix raises contamination risks for workers as they removed them over their heads.

"It doesn't matter if you're an Osaka city citizen or not. Please provide us raincoats," the city government website said.

The request comes as Japan's two emergency medicine associations issued a joint statement saying they are "already sensing the collapse of the emergency medical system".

"The number of hospitals that can accept patients suffering from a high fever and breathing problems is decreasing," the statement said, warning these patients were instead being sent to emergency clinics which had to turn away patients with other serious medical complaints.

"We fear that patients suffering from heart attacks, strokes, or multiple injuries might lose precious time in being treated," the statement said.

State of emergency

Japan has seen a relatively smaller-scale outbreak than many other countries, with 8,100 infections and 119 deaths since the first case emerged in mid-January.

But the government has now declared a state of emergency in seven regions after medical advisors warned the outbreak could grow quickly if people did not stay inside and reduce contact.

The Nikkei business daily said the fabric used for protective gear in Japan is made overseas and was difficult to manufacture domestically, while the demand overseas made securing supplies difficult.

Healthcare workers in many other countries have been forced to improvise personal protection gear because of the global shortage.

Still, the Osaka appeal left many in Japan shocked.

"This reminds me of wartime when the government asked people to donate anything that was metal," one user wrote on Twitter.

"I feel sorry for medical workers who have to work in a raincoat," said another.

Japan is already trying to plug gaps in other supplies needed to respond to the outbreak, with inmates at some prisons in Osaka and Kyoto now making protective gear, according to the justice ministry.

Supplies for hand sanitisers are also running dry, prompting the health ministry to allow the use of spirits with an alcohol proof of between 70 and 83 percent to be used at hospitals.

Kanagawa prefecture near Tokyo, meanwhile, has called on residents to donate thermometers, which are also in short supply, for use at facilities, accepting coronavirus patients with mild symptoms.