Surrounded by three to four metre-high (nine to 13 feet) concrete walls topped with barbed wire and even shards of broken glass, the compound looked more like a high-security prison than a residential block. Closed-circuit cameras were installed on nearly every corner.

Armed guards kept watch over the area. There was only one entry gate, where each visitor and vehicle was thoroughly checked.

Local residents said most of the operations were led by Chinese nationals, though some South Koreans served as middlemen. According to Amnesty International, at least 53 compounds of this kind are scattered across Cambodia.

A South Korean restaurant owner nearby said: “Many of these compounds even run their own internal canteens. Sometimes we get delivery orders for gimbap or kimchi from casinos or buildings like that. When we deliver, a Chinese man usually comes out to pick up the food.”