North Korean troops are in Russia, U.S. defense secretary says

 U.S. Defense Secretary Lloyd Austin said on Wednesday there is evidence that North Korean troops are in Russia but it remained to be seen what they would be doing there.

Austin said it would be “very, very serious” if they are preparing to fight alongside Russia in Ukraine, as Kyiv has alleged.

Secretary of Defense Lloyd J. Austin III confirmed on Wednesday that North Korea had sent troops to Russia to join the fight against Ukraine, a major shift in Moscow’s effort to win the war. Mr. Austin called the North’s presence a “very serious” escalation that would have ramifications in both Europe and Asia.

“What exactly are they doing?’’ Mr. Austin told reporters at a military base in Italy. “Left to be seen.” He gave no details about the number of troops already there or the number expected to arrive.

His statement came as American intelligence officials said they were preparing to release a trove of intelligence, including satellite photographs, that show troop ships moving from North Korea to training areas in Vladivostok on Russia’s east coast and other Russian territory further to the north. No troops have yet reached Ukraine, the intelligence officials said.

For two weeks, there have been reports of the movements, fueled by the Ukrainian and South Korean governments, that upward of 12,000 North Koreans were training to fight alongside Russian soldiers.

American officials have said they estimate that about 2,500 North Korean troops have been dispatched. But they made no estimate of how many more might follow, or even how well they might perform on territory that the North’s conscripts have never fought in, amid fellow fighters who speak a different language.

There was no immediate comment from the Kremlin. Russia has denied earlier reports on North Korea’s troop presence.

Nonetheless, both Russia and North Korea experts called it a watershed moment. Desperate not to stir up domestic resentments about the huge casualties Russia has taken — over 600,000 killed or wounded, American officials recently estimated — Mr. Putin is now reaching for mercenary forces, supplied by the same country that has sold him more than a million artillery rounds, many of them defective.

For Kim Jong-un, the North’s leader, the war in Ukraine has been a pathway out of geopolitical isolation. For the first time in decades, the North possesses assets that a major power is willing to pay for.

His longer-term plan, experts say, may be to improve the reach of his intercontinental ballistic missiles. He is eager, American intelligence agencies believe, to make it clear that his arsenal of nuclear-tipped weapons is capable of hitting American cities.

“This is the real ‘no-limits partnership,” said Victor Cha, a North Korea expert at the Center for Strategic and International Studies who was a member of President George W. Bush’s national security council. “We are in a whole different era if North Korean soldiers are dying for Putin. It will raise the ask when Kim makes demands, and Putin will give him what he wants.”

In comments to reporters on Monday, President Volodymyr Zelensky of Ukraine sought to portray North Korea’s presence as an attempt by Mr. Putin to avoid an unpopular mobilization.

“I wouldn’t say they have run out of personnel,” the Ukrainian leader said of Russia. “However, the reluctance to mobilize their own people is certainly increasing, and there are formats for mobilizing North Korean troops. This is definitely happening.”