A North Korean rocket carrying its second spy satellite exploded midair on Monday, state media reported, after its neighbors strongly rebuked its planned launch.

The North's official Korean Central News Agency said it launched a spy satellite aboard a new rocket at its main northwestern space center. But KCNA said the rocket blew up during a first-stage flight soon after liftoff due to a suspected engine problem.

Earlier Monday, North Korea had notified Japan's coast guard about its plans to launch "a satellite rocket," with a warning to exercise caution in the waters between the Korean Peninsula and China and east of the main Philippine island of Luzon during a launch window from Monday through June 3.

South Korea's Joint Chiefs of Staff later said it detected a launch trajectory believed to be of a spy satellite fired from the North's main space center at 10:44 p.m. on Monday.

But minutes later "many fragments of the projectile were detected in North Korean waters, and the U.S. and South Korea are analyzing whether it had an operational flight," the JCS added.

Japanese Prime Minister's Office earlier issued a missile alert for the island of Okinawa following North Korea's launch. The alert was lifted soon after.

Japan's NHK public television earlier reported that an image captured by a camera in northeastern China showed an orange light in the sky and then an apparent explosion a moment later.

North Korea sent its first military reconnaissance satellite into orbit in November last year as part of efforts to build a space-based surveillance network to cope with what it calls increasing U.S.-led military threats. North Korean leader Kim Jong Un later told a ruling party meeting that the country would launch three additional military spy satellites in 2024.

The November launch followed two failed liftoffs.

In the first attempt, the North Korean rocket carrying the satellite crashed into the ocean soon after liftoff. North Korean authorities said the rocket lost thrust after the separation of its first and second stages. After the second attempt, North Korea said there was an error in the emergency blasting system during the third-stage flight.

The U.N. bans North Korea from conducting any satellite launches, viewing them as covers for testing long-range missile technology. North Korea has steadfastly maintained it has the right to launch satellites and test missiles. Kim has said spy satellites will allow his military to better monitor U.S. and South Korean military activities and enhance the threat posed by its nuclear-capable missiles.

North Korea provides Japan with its launch information because Japan's coast guard coordinates and distributes maritime safety information in East Asia.

U.S. intelligence "closely monitoring and tracking" situation

The attempted launch came just hours after Seoul, Beijing and Tokyo wrapped up their first trilateral summit since 2019.

South Korea's President Yoon Suk Yeol said Monday that another satellite launch -- North Korea's fourth attempt -- would "undermine regional and global peace and stability" and urged Pyongyang not to go ahead.

The South Korean military conducted attack formation flight and strike training on Monday to demonstrate "the strong capabilities and will of our military" after North Korea notified Japan of its plans to launch a satellite by June 4.

Experts say that spy satellites could improve North Korea's intelligence-gathering capabilities, particularly over South Korea, and provide crucial data in any military conflict.

Seoul has said the North received technical help from Russia for its November satellite launch, in return for sending Moscow weapons for use in the war in Ukraine.

Kim Jong Un met President Vladimir Putin in Russia last September, and Putin suggested afterwards that his nation could help Pyongyang build satellites.

A group of Russian engineers has entered North Korea to help with the launch preparations, Yonhap reported Sunday, citing a government official.

Seoul had said on Friday that South Korean and U.S. intelligence authorities were "closely monitoring and tracking" preparations for another launch.

North Korea claims the "Malligyong-1" satellite it put into orbit in November is successfully functioning, but Seoul's intelligence agency has cast down on this claim.

Seoul's National Intelligence Service collected and analysed debris from one of Pyongyang's failed launches earlier last year, finding it had no military utility.

AFP contributed to this report.

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