Japan will have around 10 minutes to warn its citizens that a nuclear attack is coming.
But in the event it's ever targeted in this way by North Korea, people could have even less time than that to flee to safety, according to news.com.au.
The country's authorities have issued guidelines on what to do if a nuclear missile hits its shores as tensions remain high across the region.
The Cabinet Secretariat Civil Protection Portal Site reveals how the public will be notified of an impending attack under the country's J-Alert system.
The nationwide system, introduced in 2007 to warn its citizens of a disaster or threat, is designed to co-ordinate an emergency response and also provides information on what to do in the case of an evacuation.
Details of a disaster or attack are broadcast via satellite, phone and via the internet to disaster management authorities who then relay warnings via loud speakers, emergency broadcast channels and mobile alerts.
The Cabinet Secretariat Civil Protection Portal Site has seen a surge of visitors in recent weeks as fears grow over Pyongyang's nuclear and missile tests.
According to The Independent, Japan's civil defence website had 5.7 million visitors in the first 23 days of April alone.
The site makes clear while risk of a full scale invasion remains the lowest it has been in 10 years, "Japan is facing urgent new threats to peace and security and diverse situations, including the proliferation of weapons of mass destruction and ballistic missiles."
However if a missile attack does take place, the Protecting Ourselves Against Armed Attacks and Terrorism document found on the site urges people to find a strong concrete building to find safety or head underground.
People should also take cover under something like a table while avoiding windows and doors.
Citing a missile launch in February last year which took 10 minutes to travel 1600km and fly over Okinawa, the Japan Times reveals just how quickly it could hit the island.
The advice comes as prefectural disaster and crisis officials held a meeting in Tokyo last week where they were urged to make additional plans to establish their own response teams and plans.
Osaka Mayor Hirofumi Yoshimura announced he will establish a response team in the event of a North Korean attack and said it would include officials involved in crisis management, the Japan Times reported.
But Yoshimura warned there would be almost no time to respond and people may not have as much time as they think to escape to safety.
"A missile may not be detected as soon as it leaves the launch pad and that could take several minutes," he said.
"Depending on the case, the warnings and alarms might only sound four or five minutes before a missile arrives."
'Point of no return'
Japan isn't the only world power concerned about North Korea's nuclear ambitions.
US President Donald Trump told members of the United Nations Security Council at the White House that the "status quo" on North Korea is "unacceptable" and urged it to impose additional and stronger sanctions on Pyongyang.
And China's official newspaper Global Times, controlled by the ruling Communist Party, has also warned North Korea will cross the point of no return if it carries out another nuclear test.
Similar concerns were echoed as top nuclear envoys from Japan, South Korea and the United States met in Tokyo yesterday and vowed "stern action" against any fresh North Korean provocations.
US special representative Joseph Yun said he discussed American policy to "enhance pressure" on Pyongyang "because we really do not believe that North Korea is ready to engage us towards denuclearisation".
Meanwhile North Korea held major live-fire drills to mark the 85th founding anniversary of its military.
South Korea's Yonhap news agency cited a government source as saying the exercise was the North's "largest ever".
"Signs are detected that North Korea's military is conducting a large-scale drill around the eastern port city of Wonsan on the anniversary," a source told Yonhap News.