The Republic of Korea and Japan signed a long-delayed agreement on sharing military intelligence on Wednesday, despite public opposition in Seoul, ensuring the free exchange of information among the two countries and their ally the United States.

Experts said the move, together with other recent activities by Seoul, reflects a spreading Cold War mentality that could heighten tension on the Korean Peninsula and test Seoul's relationship with Beijing, since the sharing of intelligence could relate to China.

The General Security of Military Information Agreement, signed on Wednesday, allows the ROK and Japan to directly share information about the Democratic People's Republic of Korea without first going through US intelligence.