North Korean leader Kim Jong Un was to tour a Russian aircraft plant that builds fighter jets and then visit the country’s Pacific Fleet, but his exact whereabouts remained uncertain, as South Korea on Thursday expressed “deep concern and regret” that his visit has focused on expanding military cooperation.

South Korea’s Foreign Ministry pointed out that Kim’s delegation includes several people sanctioned by the UN for involvement in illicit North Korean weapons development, including Army Marshal Ri Pyong Chol and Jo Chun Yong, a ruling party official who handles munitions policies.