The March 15 concert commemorated the 20th anniversary of diplomatic relations between the two nations and took place at Hanoi’s National Conference Center as a collaborative effort between the Korean Broadcasting System (KBS) and Vietnam Television.

A number of top K-pop stars participated including Super Junior, CN Blue, and Beast, as well as local artists.

Though the concert itself was deemed a huge success by both Korean and Vietnamese media, according to Vietnam’s Tuoitre news service, many local K-pop fans felt locked out of the event.

Initially, all tickets to the concert were to be given away free.

The Conference Center seats 4,000, but as late as March 15 there was no clear announcement as to where and how people could obtain the free tickets.

In the end, a large number became available from online sites, where they cost as much as 7 million dong ($336) for a pair, well out of the reach of the majority of Vietnamese.

Some fans went directly to Vietnam Television to demand tickets but were told none were left. When other fans called the station directly, no one answered.

Consequently, a huge crowd showed up at the hall the night of the concert hoping to get in, and, as it turned out, a large number of seats were empty during the performance.

Commenters on social media sites accused authorities of giving tickets to black marketers. One commenter, writing on KBS’s Vietnamese Facebook page, said the problem could have been solved if “the organizers had just sold the tickets” to the public.

In other Vietnam-related K-pop news, pop star Rain, who is currently fulfilling his obligatory military service, took time out from his duties to perform at the Ho Chi Minh City Military Theater on March 19 and the Hanoi Opera House on March 21.

He was joined by another K-pop star, Park Hyo-shin, who is also in the army.

They were accompanied by the South Korean National Military Symphony Orchestra and 17 traditional musicians.