Former World Boxing Council (WBC) super flyweight champion Cho In-ju failed to regain the title at a fight Sunday as current champion Hong Chang-su knocked out Cho, 45 seconds into the fifth round.

The 27-year-old Hong, a third-generation pro-Pyongyang Korean living in Japan, retained the title for the second time at the fight held at a Seoul hotel.

The 31-year-old Cho dominated the fight in the first two rounds but lost control in the third, and was unable to stand on his feet in the fifth round when the 27-year-old Hong landed a right-hand straight on the challenger's chin.

Cho had lost the WBC title to Hong by unanimous decision in Osaka last August. Hong successfully defended the title against a Japanese challenger last December.

Taking into account this fight, Hong has a record of 24-1-2 with six knockouts, and Cho is 18-2 with seven knockouts.

The fight between Cho and Hong has attracted widespread media attention as a ''bout in the ring between South and North Korea.''

A total of 250 of Hong's fans from the General Association of Korean Residents in Japan (Chongryun) rooted for the compatriot at the match.