North Korea is preparing to send Russia more than 100 artillery systems – originally designed to flatten Seoul – to be used in its war against Ukraine.

The 170mm M1989 Koksan howitzers, among the longest-range artillery systems in the world, are known as “juche cannons”, and were built to pound the South Korean capital in the event of a conflict.

Kyrylo Budano, Ukraine’s military intelligence chief, said that Pyongyang was gearing up to double the number of artillery systems it has sent to the border region of Kursk.

The fresh deliveries come amid reports that North Korean soldiers have been withdrawn from sections of the front line to rebuild and regroup, while more troops are expected to be deployed soon.

Lt Gen Budanov said that over the past three months, Kim Jong-un had already given Moscow at least 120 North Korean-made M1989 Koksans, as well as another 120 of its M1991 multiple-launch rocket systems.

Speaking to defence outlet The Warzone, he said Pyongyang was preparing to send another tranche of at least the same amount, with open source analysts suggesting some were already on route.

The M1989 Koksan is a 40-ton self-propelled gun that first appeared during a military parade in 1989. The term “juche” is used in North Korean propaganda to describe its state ideology of freedom and self-reliance.

Using standard shells, the cannons can strike targets over 25 miles away. Gen Budanov said North Korean troops were training their Russian counterparts to use them and they had begun firing them in combat.

In late December, footage showed a train transporting a convoy of at least 10 M1989 Koksans to Russia, their 25ft-long barrels on full display, with little to no camouflage hiding them from enemy strikes.

By Jan 7, they appeared to have arrived as footage emerged of them on the battlefield in Kursk. In the video, a North Korean soldier called the artillery system a “gift” from Kim to his soldiers abroad.

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Pyongyang has deep reserves of artillery systems and ammunition that have been stockpiled largely to threaten and prepare for a conflict with its rival, South Korea.

North Korea deployed 11,000 soldiers to its ally Russia in late October to help Moscow expel Kyiv’s troops from the Kursk border region after Ukraine’s surprise incursion in August.

South Korea joint chiefs of staff said on Friday that the North was preparing for an additional dispatch of troops to Russia. US officials, speaking to The New York Times, said the fresh reinforcements could arrive within two months.

Neither Moscow nor Pyongyang – which signed a “mutual military assistance” deal last June – have confirmed Kim Jong-un’s participation in the war, despite two North Korean prisoners of war being captured by Kyiv.

On Monday, Ukrainian reports emerged that North Korean soldiers appear to have temporarily withdrawn from one of the axes of the front in Kursk.

A Special Operations Forces (SOF) spokesman confirmed to the Kyiv Independent that Pyongyang’s troops had retreated from some of their positions and are probably regrouping after suffering significant losses.

The statement came after a Ukrainian commander told Sky News that North Korean troops had, for now, withdrawn from the front line in the Russian border region.

The commander, who goes by his call sign “Puls”, said they were probably trying to learn lessons from their mistakes, tending to their wounded or waiting for reinforcements.

“I think they’ll be back soon” he said, while also noting the high motivation among the foreign soldiers despite heavy losses.

Puls also described how North Korean soldiers were an easy target as they appeared to be unaware of the threats from drones and modern artillery and had been attacked on foot in large groups “like in World War II”.

His claims echo those of Ukrainian commanders and analysts who say the troops have not been trained in modern warfare and are being used by their Russian allies as cannon fodder in “human wave” attacks.

About 1,000 North Korean soldiers have been killed and 3,000 wounded while fighting in Russia’s war against Ukraine, the BBC reported last week, citing unnamed Western officials.