China on Tuesday imposed sanctions on five U.S.-linked subsidiaries of South Korea’s Hanwha Ocean, sending the shipbuilder’s shares sharply lower amid escalating trade frictions between the world’s two largest economies.

The sanctions, announced by the Ministry of Commerce, coincide with the implementation of additional port feestargeting U.S. and Chinese vessels, although China has exempted ships built domestically.

According to the ministry, organizations and individuals in China are barred from engaging in any transactions, cooperation, or related activities with the sanctioned Hanwha entities.

The ministry statement said, “Hanwha Ocean’s U.S.-related subsidiaries have assisted and supported the U.S. government’s relevant investigative activities, thereby jeopardizing China’s sovereignty, security, and developmental interests,” without providing further details.