Do companies controlled by central enterprises in Hong Kong belong to state-owned enterprises?

Belong to.

Companies controlled by central enterprises in China Mainland and Hongkong are regarded as state-owned enterprises. Central enterprises refer to large state-owned enterprises directly managed by the central government of China, and state-owned enterprises refer to enterprises owned or controlled by the state. In Hongkong, China, some central enterprises have local subsidiaries or holding companies, which are regarded as part of state-owned enterprises. For example, China Resources, China Merchants, China Travel Service and other central enterprises have subsidiaries or holding companies in China Mainland and Hongkong, which are considered as key state-owned central enterprises and one of the "53" central enterprises.

The development of these central enterprises in China Mainland and Hong Kong is based in Hong Kong, but they will also have headquarters in other places. Generally speaking, companies controlled by central enterprises in China and Hongkong are considered as state-owned enterprises.