The assessment came two days after North Korea confirmed for the first time that it had sent combat troops to help Russia recapture parts of the Kursk region, which it lost control of to a surprise Ukrainian incursion last year.

Russia's success removes another barrier to a peace deal Moscow was reluctant to conclude with so many enemy troops on its soil.

Russian President Vladimir Putin declared a three-day ceasefire in the war with Ukraine next month to celebrate the Soviet Union’s victory over Nazi Germany during World War II.