Residents expressed discontent with the move, questioning the transparency of the decision-making process as well as the potential risks to their health.

The police established a special investigation team, which focuses on whether water bottles and eggs can be considered "hazardous tools" or the demonstration itself broke relevant laws.

Residents of Seongju plan to hold a rally in Seoul on Thursday.

Kang, however, did not directly express his opinion on whether the so-called "outsiders" were involved in the violent protests.

"We are currently finding out details of non-resident protesters on the day," Kang said. "But there are no investigations under way (on specific organizations or individuals).

"Rather than define them as outsiders, I believe such people can be sorted as we start investigations into wrongdoings," the police chief added. (Yonhap)