A Japanese newspaper said that the use of suspected North Korean missiles in Russia's war against Ukraine sharply increased since Moscow and Pyongyang signed a comprehensive strategic partnership agreement last year.

Japan's Yomiuri Shimbun daily said on Sunday that its analysis of data by the Center for Strategic and International Studies (CSIS) found that the number of suspected North Korean missiles fired by the Russian military in the Ukraine war increased significantly in the second half of last year.

According to the report, in the war in Ukraine, Russia is estimated to have launched eight North Korean missiles, presumed to be short-range ballistic missiles such as the KN-23, in the first half of last year, but the number increased over nine times to 74 in the second half.

Yomiuri said that there appear to be more suspected North Korean missiles that the CSIS has not been able to compile, assessing that North Korea and Russia have strengthened cooperation in the war under the strategic partnership agreement.

The Treaty on Comprehensive Strategic Partnership, a security and defense treaty between the two nations, says that if either country is invaded, the other one must provide military and other assistance.