South Korea's trade minister said on Monday that Seoul had complained to the World Trade Organization about China's retaliation against South Korean companies over the deployment of a U.S. missile defense system.

"We have notified the WTO that China may be in violation of some trade agreements," Trade Minister Joo Hyung-hwan told the National Assembly in response to questions about China's reaction to the deployment of the Terminal High Altitude Area Defense (THAAD) system in South Korea.

Joo said the complaint was made last week after China imposed restrictions on South Korean companies in the tourism and distribution sectors.