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.

WASHINGTON—The U.S. said thousands of North Korean troops are being trained in Russia and might be used to reinforce Moscow’s military offensive in Ukraine.At least 3,000 North Korean soldiers arrived by ship earlier this month at the Russian port of Vladivostok and moved to several training sites in eastern Russia,

South Korea’s spy chief has told lawmakers that North Korea has sent another 1,500 troops to Russia to support its war against Ukraine.