Security has been tightened at Yonsei University after a man wearing only a mask and no clothes was reported three times over the past two months for sexually harassing students and others near the campus.

In a dormitory notice issued yesterday (Aug. 20), Yonsei University stated, "Safety-related incidents have occurred due to unauthorized entry by outsiders within the dormitory zone." The university added, "To prevent recurrence and create a safe living environment, we are temporarily closing the access gate leading to Ansan Mountain behind the Muak Residence Hall 1."

This means the university will restrict outsider access by shutting down some of the entrance gates connected to the Ansan hiking trails linked to Yonsei University's Sinchon Campus.

Previously, at around 10 p.m. on the 19th, a report was filed that a naked man wearing only a black mask appeared near the dormitories on the Sinchon Campus, sexually harassed a victim who was a Yonsei student, and fled.

Police have launched a manhunt for the unidentified suspect on charges including forcible indecent act and public indecency. It was confirmed that similar reports had been filed in June and July as well.

On the evening of June 12, a naked, masked man forcibly harassed a passerby on the Ansan Jarak-gil walking trail. On July 21, a man matching the same description was reported after a passerby spotted him hiding in the bushes near a similar location.

Given the identical appearance and method of the crimes, police are giving weight to the possibility that they were committed by the same culprit.

More than two months have passed since the initial report was filed, but police explained that the incidents occurred in the border area between the university and Ansan Jarak-gil, and there are not enough CCTV cameras to trace the route of the suspect, who is believed to have escaped via the Ansan mountain paths.

Police are analyzing footage capturing the man's appearance with the cooperation of Yonsei University.

Reported by Kim Taewon | Video by Ryu Jisoo | Graphics by Yang Hyemin | Produced by SBS Digital News