U.S. Defense Secretary Lloyd Austin has offered the first confirmation by Washington that North Korean troops are in Russia, following claims by Kyiv and Seoul that Pyongyang is dispatching thousands of soldiers to fight alongside Russian forces in the war against Ukraine.

"There is evidence that there are (North Korean) troops in Russia," Austin said Wednesday in televised comments from Rome.

But he said that it remained to be seen what exactly the North Korean troops were doing in Russia.