• NATO Secretary General Mark Rutte said North Korea had sent troops to fight Russia.
• He portrayed the alliance as a sign of weakness and said Putin could not sustain the invasion alone.
• Ukraine has said it expects to encounter North Korean troops on the battlefield within days.

The NATO chief said Russia could not sustain its invasion of Ukraine without North Korean troops.

Mark Rutte said at a news conference on Monday that North Korean troops were stationed in Russia's Kursk region, where Ukraine occupies territory.

He cited information from South Korean intelligence, its defense ministry and NATO allies.

“Over 600,000 Russian soldiers have been killed or wounded in Putin's war, and he is unable to sustain his assault in Ukraine without foreign support,” he said, referring to Russian President Vladimir Putin.

He called the deployment a sign of “growing desperation” in the war, which has already been going on for around two and a half years.

Ukrainian President Volodymyr Zelensky said over the weekend he expected to see North Korean troops in combat within days.

It would be the first time that another country had committed ground troops to the main war effort in Ukraine. Both sides have long received weapons and advice from their allies.

Last Thursday, Zelensky said he had information indicating that North Korea was preparing to send 10,000 troops to the occupied territories of Ukraine.

The move alarmed South Korean authorities, who condemned the operation last week. They threatened to send weapons to Ukraine as part of a series of gradual countermeasures.

Rutte said NATO had called on both Russia and North Korea to withdraw immediately, citing risks to both Indo-Pacific and Euro-Atlantic security.

“It undermines peace on the Korean Peninsula and fuels Russia’s war against Ukraine,” he said.

Putin, for his part, appeared unfazed by external criticism last Friday and said it was Russia's “sovereign decision” whether to send North Korean troops.

“This is our business,” he said, according to Reuters.