Items are piling up at the Kaesong Industrial Complex (KIC) in a sign that North Korea is “illicitly operating” some parts of the inter-Korean economic zone, South Korea's unification ministry said Tuesday, a day after slamming the North for what it called improper use of South Korean assets.

The remarks come after the ROK military reported detecting the movement of unknown vehicles in the KIC earlier this year. According to a ministry official on Tuesday, South Korea has detected vehicles in the economic zone on multiple occasions since then.