Approximately 1,000 North Korean troops have been killed in Russia’s Kursk region while fighting Ukraine on Vladimir Putin’s behalf, officials say.

Anonymous Western sources told the BBC that, as of mid-January, there have been 4,000 casualties among the 11,000-strong contingency who were sent to help Putin’s troops fight off Ukraine’s attack in the Russian region of Kursk.

The overall casualty rate – a stat which includes those killed, wounded, missing or captured – is allegedly 36% among the North Korean troops.

That’s much higher than the previous estimates from South Korea’s spy agency, which claimed around 300 North Korean soldiers have been killed in the war and 2,700 have been injured.

Officials also told the broadcaster that it’s not clear where the soldiers are being treated, or if they will be replaced.

Russia has not confirmed or denied North Korean troops are fighting alongside its own since they were first deployed in autumn.

Putin arranged a mutual defence agreement with his North Korean counterpart Kim Jong Un last summer, and both countries agreed to defend the other if attacked by a third party.

It’s thought Ukraine’s incursion into Kursk in August was seen as an attack on Russia – so Putin was able to call on North Korean troops to bolster his beleaguered army to defend the region.

Putin has been ploughing through his own soldiers, forcing them forwards on the frontline using what UK prime minister Keir Starmer described as “meat-grinder” tactics.

The UK’s ministry of defence said earlier this month Russia is estimated to have suffered more than 790,000 casualties since the war began.

The MoD also warned that North Korean – also known as DPRK – troops were struggling to integrate with their Russian peers.

The intelligence officers said: “Russian and DPRK forces are almost certainly experiencing interoperability difficulties.

“The two forces do not share a common language and DPRK troops almost certainly have difficulties integrating into Russia’s command and control structure.”

North Korean troops have “highly likely sustained significant combat casualties” already and “only achieved tactical gains”, the intelligence claimed in the latest update on X.

Ukrainian president Volodymyr Zelenskyy confirmed earlier this month that his troops had seized two North Korean soldiers in Kursk for the first time.

He offered a prisoner swap, hoping to secure the release of Ukrainians held by Russia.

“Ukraine is ready to hand over Kim Jong Un’s soldiers to him if he can organise their exchange for our warriors who are being held captive in Russia,” Zelenskyy said.

North Korea has claimed the US is to blame for the concept of the “nuclear threat” in a bizarre statement.

It comes after reports US president Joe Biden approved a classified strategic plan back in March, calling for a focus on China instead of Russia, as a strong nuclear opponent.

Supposedly US forces were urged to prepare for a possible coordinated attack between Russia, China and North Korea.

In a statement reported by the Russian state news agency TASS, North Korea’s foreign ministry appeared to respond by saying it “keeps a close eye on the behaviour” of the US.

It claimed Washington DC “continues to fabricate someone else’s ‘nuclear threat’” while being “obsessed with ensuring unilateral nuclear superiority”.

The ministry said: “We express concern about it as we strongly oppose and reject it.

“The move to update the nuclear policy of the US – a country that has the largest nuclear weapon arsenal in the world – will have a significant negative impact on the security situation and the nuclear disarmament system.”

According to the International Campaign to Abolish Nuclear Weapons, Russia actually has the most confirmed nuclear weapons with over 5,889 nuclear war heads.

The US comes in second, with 5,224 nuclear weapons.

All other countries known to have nuclear weapons – including the UK and North Korea – have under 500 in comparison.

China comes in third place, with 410 nuclear warheads.

Still, the North Korean foreign ministry claimed: “The US likes to speak about ‘nuclear threats’ from others without any context, while it is the US that is the most irresponsible player and the rogue state provoking a nuclear arms race and increasing the likelihood of a global nuclear conflict.

“Had the US refrained from creating and using nuclear weapons, the concept of nuclear threat would never have emerged.”

Moscow has repeatedly threatened to deploy nuclear weapons against the West ever since invading Ukraine in 2022 – the US and Europe have offered financial and military backing to Kyiv over the last two years.

At the end of July, Vladimir Putin said it would take just 10 minutes for Russian missiles to hit their intended target.

As Reuters reported, the president claimed: “We will take mirror measures to deploy, taking into account the actions of the United States, its satellites in Europe and in other regions of the world.”