Last month, Seoul announced that it would use firearms if necessary against Chinese vessels illegally fishing in Korean waters.
"We will actively respond to Chinese fishing boats that obstruct justice by using all possible means if needed such as directly hitting and gaining control of those Chinese fishing boats as well as firing common weapons," South Korea’s deputy coast guard chief, Lee Choon-jae, told reporters.
On Wednesday, coast guard officials confirmed it had made good on that threat, according to Asia Times.
Senior official Kim Jung-Shik told Yonhap news agency that the order was given to fire machine guns on 30 Chinese fishing boats in the Yellow Sea.
"They tried to ram our ships although we repeatedly warned them," Kim said.
"I thought our officers would be in danger if I allowed any more resistance so we ended up using the crew service weapon."
Shots were initially fired into the air before the coastguard targeted the bows of the vessels. The coastguard also seized two Chinese fishing boats.
No one is injured in the incident.
The Chinese ministry of foreign affairs released a statement expressing "strong dissatisfaction" over the incident.
"We have lodged multiple solemn representations to Korea on its coast guards’ violent enforcement techniques," the statement reads, according to the Financial Times.
Last month, three Chinese fishermen were killed in a fire on their boat after a South Korean coast guard crew threw flash grenades into their vessel, according to a South Korean official.
"We hope South Korea can start from the perspective of the broader situation in bilateral relations and calmly and rationally handle the relevant issue," spokesman Geng Shuang told a news briefing in Beijing.
While small wooden Chinese ships have been tolerated in the past, officials claim that these have been replaced with larger steel boats that allegedly engage in massive bottom-trawling operations.