Ongjin County in Incheon, which governs Yeonpyeong and nearby fishing activities, said it decided not to take any disciplinary or administrative measures against the South Koreans, saying their action was akin to ordinary people making a citizen arrest of lawbreakers.

"We have internally reached a conclusion not to punish the South Korean fishermen," said a county official, asking not to be named. "Still, because areas near the NLL are dangerous and lie too close to North Korea, we hope no other fishermen try to seize Chinese boats on their own."

Related to the decision, in 2005, South Korean crewmen seized four Chinese fishing boats that had crossed the NLL, but they were not punished.

The Coast Guard, meanwhile, said it will investigate further details of the incident by questioning the local fishermen next month, regardless of whether the administrative measure will take place.

Illegal fishing by Chinese fishermen is a troublesome issue in the country as it has severely damaged the livelihood of South Korean fishermen operating in the Yellow Sea.

Chinese fishing boats often cross into South Korean waters in the Yellow Sea during peak crab season in search of bigger hauls, regularly leading to crackdowns by the South Korean Coast Guard. (Yonhap)