State-broadcaster Korean Broadcasting System issued an apology after sparking controversy by airing the opera "Madama Butterfly" on National Liberation Day.

Aug. 15 is celebrated as National Liberation Day in Korea, commemorating the nation's liberation from Japan in 1945. Early Thursday, KBS aired "Madama Butterfly," a Giacomo Puccini opera set in Japan, as part of its liberal arts program, "KBS Relay Seat."

The opera, set in Japan's Nagasaki shortly after World War II, tells the tragic love story of a Japanese geisha and an American naval officer. The opera includes characters dressed in kimono and features Japan's national anthem, which many viewers found particularly inappropriate for airing on National Liberation Day.

Numerous complaints were posted on the KBS viewers' petition board, including a comment that said, "I feel I must file this petition to avoid being ashamed in front of the independence activists on National Liberation Day." Another viewer wrote, "Before discussing the freedom of art, how could you broadcast the national anthem, attire and art of the country that took away our sovereignty on our national day of celebration?"

As the controversy grew, KBS issued a formal apology.

"The performance was originally recorded on June 29 and was scheduled to air late last month, but the broadcast was delayed due to the Olympic coverage, leading to 'Madama Butterfly' being aired in the early hours of National Liberation Day," the broadcaster said. The performance by Korea's Nuova Opera Company was staged as part of this year's Korea Opera Festival.

KBS continued that the production team failed to check the appropriateness of the rescheduled broadcast and offered a further apology. The broadcaster also announced that the second part of "Madama Butterfly," which was scheduled to air early Friday, would be replaced with a different performance broadcast.