U.S. Says North Korean Troops Are in Russia to Aid Fight Against Ukraine

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.