FC Seoul have apologized after fans on social media accused the K League 1 side of using sex dolls to help fill the space in their empty stadium.

The top flight in South Korea is among the leagues to have returned amid the coronavirus pandemic, with the Bundesliga in Germany having also resumed this weekend.

With matches being played behind closed doors, several teams have been finding novel ways to decorate their stadia.

Seoul said their perceived faux pas, which was pointed out by several users on social media - with the mannequins supposedly holding up advertising signs for adult streaming sites, was due to a mix-up with the manufacturer.

"We would like to apologize to our fans. We're genuinely sorry to our fans about the installation of the mannequins at our game on May 17," read a statement from Seoul, who defeated Gwangju 1-0 at the Seoul World Cup stadium on Sunday.

"We confirmed from the start that the mannequins we installed in the stands had no relation to the adult toys, even though they do indeed resemble real humans.

"We had them supplied by a company and they informed us that the mannequins are designed for displaying apparel and fashion products. We confirmed with them on numerous occasions to make sure that the mannequins are not adult toys.

"[The supplier] has been distributing some of the mannequin products to another business...and in the process of return and exchange of the products between them, the installation at our stadium included some products with messages in text that are related to the adult toys.

"That was a problem on our employees who couldn't check every detail of everything that was installed. That is an inexcusable mistake on our part."