The officials from the West Sea Fisheries Supervision Office, which is affiliated with the Ministry for Food, Agriculture, Forestry and Fisheries, boarded the vessel 44 miles northwest of Heuksan Island in the Yellow Sea about 2:30 a.m., Yonhap News Agency reported.
The Chinese boat was suspected of fishing illegally.
Upon boarding the ship, the South Korean officials allegedly were attacked by the Chinese fishermen, who were armed with knives and scythes, Yonhap said.
One official fell into the sea after being hit with a blunt object. The other three sustained severe and minor injuries to their heads, arms and legs.
The four were air-lifted to a hospital in Mokpo; it was not immediately known whether their injuries were life-threatening.
The Korean coast guard seized the fishing boat and took the nine fishermen aboard into custody, officials said.
China's Department of Consular Affairs of the Ministry of Foreign Affairs was verifying the incident and called on South Korea to ensure the rights of the fishermen, China's Xinhua News Agency reported.
China will work with South Korea to resolve the issue, a Chinese official said.
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