North Korea remains totally free of the coronavirus, a senior health official in Pyongyang has insisted, despite mounting scepticism overseas as confirmed global infections near one million.

The already isolated, nuclear-armed North quickly shut down its borders after the virus was first detected in neighbouring China in January, and imposed strict containment measures.

Pak Myong Su, director of the anti-epidemic department of the North's Central Emergency Anti-epidemic Headquarters, insisted that the efforts had been completely successful.

"Not one single person has been infected with the novel coronavirus in our country so far," Pak told AFP.

"We have carried out preemptive and scientific measures such as inspections and quarantine for all personnel entering our country and thoroughly disinfecting all goods, as well as closing borders and blocking sea and air lanes."

Nearly every other country has reported coronavirus cases, with the World Health Organization saying on Wednesday that there were nearly one million confirmed infections globally.

Aside from China, South Korea endured one of the worst early outbreaks of the virus, which has claimed more than 45,000 lives around the world.

Experts have said the North is particularly vulnerable to the virus because of its weak medical system, and defectors have accused Pyongyang of covering up an outbreak.

The top US military commander in South Korea, General Robert Abrams, said last month he was "fairly certain" the North had confirmed cases of the virus.

US President Donald Trump also said North Korea "is going through something" and offered "cooperation in the anti-epidemic work", in a personal letter to North Korean leader Kim Jong Un.

And Choi Jung-hun, a former North Korean doctor who fled to the South in 2012, told AFP: "I heard there are many deaths in North Korea but the authorities are not saying that it's caused by the coronavirus."

'Strict control'

As part of its anti-virus efforts Pyongyang put thousands of its own people and hundreds of foreigners -- including diplomats -- into isolation and mounted disinfection drives, with state media constantly exhorting citizens to obey health directives.

Published images have shown universal face mask use, with the exception of leader Kim Jong Un, who has never been seen wearing one, even though for several weeks the officers alongside him when he supervised firing exercises donned black coverings.

More recently his aides have also been seen without face masks, although defector Choi said that did not signal the North's containment efforts had been widely successful.

"Everyone accompanying Kim Jong Un is under strict control and safe from any virus threats," said Choi.

Pyongyang -- which is subject to multiple international sanctions over its nuclear and ballistic missile programmes -- has sought virus-related aid.

In February, Russia's foreign ministry said it provided Pyongyang with 1,500 coronavirus diagnostic test kits at its request "due to the persisting risk of the new COVID-19".

The United Nations has granted sanctions exemptions to relief groups including Doctors without Borders and UNICEF on items such as diagnostic kits, face masks, protective equipment and disinfectants.

UNICEF confirmed its shipment of supplies -- requested by the North's health ministry -- arrived in Pyongyang overland from China last week.

The World Health Organisation plans to spend $900,000 to support Pyongyang's coronavirus response activities, according to data posted on the UN Office for the Coordination of Humanitarian Affairs website. (AFP)