Emergency services would not confirm the reported deaths, but fire services told AFP that dozens may have been trapped in the debris when the ceiling of the building caved in at a resort complex being used for a freshman orientation.
The collapse appeared to have been caused by heavy snow which piled up on the ceiling of the auditorium, they said.
Yonhap said three students had been killed, while the YTN television news channel quoted local police as saying two people had been confirmed dead.
Several hundred students were taking part in the freshman event and many of those were attending a concert in the building when it collapsed at around 9:15pm (1215 GMT), Yonhap said.
The resort was in an area that has experienced exceptionally heavy snowfall over the past week.
All the students were from a foreign language college in the southern city of Busan.