Story highlights

NEW: South Korea has seized the ship and its nine sailors

South Korea: The fishermen are suspected of fishing illegally in the Yellow Sea

Members of the South Korean coast guard board a Chinese ship to investigate

One person on board stabs two commandos, killing one, the coast guard says

Seoul, South Korea CNN  — 

A South Korean coast guard commando was stabbed to death and another injured Monday after they boarded a Chinese fishing vessel they suspected of fishing illegally in the Yellow Sea, the coast guard and a South Korean news agency said Monday.

The incident triggered a swift diplomatic response, with the South Korean Foreign Ministry calling in the Chinese ambassador to South Korea to protest, the Yonhap news agency reported. First Vice Foreign Minister Park Suk-hwan “strongly demanded the Chinese government strictly clamp down on illegal fishing and the illegal acts of Chinese fishermen,” the news agency quoted him as saying.

South Korea said it had seized the Chinese ship and nine sailors aboard, Yonhap reported.

A spokesman for China’s Ministry of Foreign Affairs said Monday that the country is “closely following the case.”

“China is ready to work closely with the (South Korean) side to handle the case properly,” spokesman Liu Weimin said. “The two countries had signed relevant fishery agreements. … Competent authorities have taken measures to educate Chinese fishermen and management of outbound fishing boats to prohibit cross-border fishing and irregularities.

“At the same time,” Liu added, “we hope the (South Korean) side will fully protect the rights and interests of Chinese fishermen and provide them with due humanitarian treatment.”

The incident started after South Korean commandos boarded the Chinese ship. The captain of that ship “suddenly broke a window pane on the ship” and stabbed one commando several times with a piece of broken glass, Yonhap reported. That commando later died; another was hurt.

South Korean authorities took the ship toward the port at Incheon, west of Seoul.

The Yellow Sea has been a point of contention for several Asian countries, most notably North and South Korea who have long disagreed on whose waters end where.

The South Korean coast guard has stopped hundreds of Chinese boats this year on suspicion of illegal fishing in the sea.

The waters, which are important fishing and crab grounds, are also frequently crowded with boats from China. And disputes over fishing rights have resulted in dozens of boat seizures.

CNN’s Chi Chi Zhang and Tim Lister contributed to this report.