He said Japan's government has routinely coordinated with representatives of tens of thousands of Japanese residents in South Korea on contingency plans.
North Korea, still technically at war with the South after their 1950-53 conflict ended in a truce but not a treaty, has on occasion conducted missile or nuclear tests to coincide with big political events and often threatens the United States, South Korea and Japan.
(AP Photo/Wong Maye-E). North Korean schoolgirls perform at the Mangyongdae Children's Palace on Friday, April 14, 2017, in Pyongyang, North Korea.
On Friday, the North's military issued a statement threatening the "toughest counteraction" to destroy American military bases and South Korea's presidential compound in case of aggression against Pyongyang.
Fears that Pyongyang would carry out a sixth nuclear test rose before the celebrations for the 105th anniversary of the birth of the country's founder, Kim Il Sung, on Saturday.
North Korean state television showed Kim, wearing a black suit and white shirt, stepped out of a black limousine and saluted his honor guard before walking down a red carpet.
Missiles are displayed during a parade at Kim Il-sung Square in Pyongyang on Saturday.
Weapons analysts said they believed some of the missiles on display were new types of intercontinental ballistic missiles (ICBM).
Other military hardware at the parade included tanks, multiple rocket launchers and artillery, as well as a solid-fuel missile created to be fired from submarines. Also on display was a powerful midrange missile, which outside analysts call "Musudan", and which can potentially reach USA air bases in Guam.
During the pomp and circumstance at Kim II Sung square, citizens showed their revolutionary fervor with choreographed performances while vehicles displaying North Korea's military arsenal rolled by.
North Korea denounced the United States for bringing "huge nuclear strategic assets" to the region as the Carl Vinson strike group with a flag-ship nuclear-powered aircraft carrier steamed closer, and said it stood ready to strike back.
The North's display of the strategic weapons to the world is apparently aimed at boasting of its military firepower as the USA continues to deploy high-profile defense assets near the peninsula. Last week, the USA attacked a Syrian airfield for the first time with cruise missiles and this week dropped the world's largest non-nuclear bomb on Afghanistan.
Other senior officials joining Kim at the podium included Kim Won Hong, who the South Korean government had said earlier this year was sacked from his job as state security minister, presumably over corruption.
Kim Jong Un, a 30-something leader who took power in late 2011 after the death of his father, Kim Jong Il, emphasizes nuclear weapons as the foundation of his national defense strategy.
Trump has repeatedly said he will prevent Pyongyang from its goal of developing a nuclear-tipped ballistic missile capable of reaching the mainland United States.
In his annual New Year's address, Kim said North Korea's preparations for an ICBM launch had "reached the final stage".
Satellite photographs this week have shown activity around the North's Punggye-ri nuclear test site, which could be taken to indicate another underground nuclear test is imminent.
North Korea conducted two such tests a year ago alone, which analysts say would have taken the country a step forward in gaining the knowledge to make nuclear weapons small enough to fit on long-range missiles.
It has carried out five nuclear tests - two of them past year - and multiple missile launches, one of which saw three rockets come down in waters provocatively close to Japan last month. The move is seen as an apparent show of force against the U.S. that has dispatched its carrier strike group USS Carl Vinson to the Korean peninsula following the North's latest missile test in April.
The missile failure also came hours ahead of a visit by US Vice President Mike Pence to South Korea where the North's weapons programme will top the agenda.
However, U.S. officials told The Associated Press on Friday that the Trump administration has settled on a policy that will emphasize on increasing pressure on Pyongyang with the help of China, North Korea's only major ally, instead of military options or trying to overthrow Kim's leadership.
In this image made from video broadcast by North Korean broadcaster.
Pyongyang has also expressed anger over the ongoing annual spring military exercises the US holds with South Korea, which it considers a rehearsal for invasion.