Wales winger Rabbi Matondo has apologised after being pictured wearing the shirt of his German club's biggest rivals.

The 19-year-old Schalke player trained in a Borussia Dortmund top.

Matondo says he naively wore "close friend" Jadon Sancho's shirt in a private gym session.

"I just want to say how deeply sorry I am to everyone offended and upset by my actions," wrote Matondo on social media.

The original picture has been deleted, but it has been widely circulated.

Matondo stated: "Addressing the pictures circulated on social media of me in the shirt of our biggest rivals, I am very sad and disappointed in myself for letting everyone associated with Schalke down.

"I want to clear this situation up and most importantly to apologise to everyone at the club - in particular our incredible fans. Causing such hurt and upset was absolutely not my intention."

Matondo, who joined Schalke from Manchester City on a four-and-a-half-year deal in January 2019, said he was "naive" to wear England international Sancho's Dortmund shirt.

"I wore it because it was Jadon's. And not because of anything to do with Dortmund," Matondo explained.

"I did this not thinking of the consequences and how upset I would make a lot of people. There's no excuse for my immaturity.

"I just want to say how deeply sorry I am to everyone offended and upset by my actions.

"I can only promise everyone at the club that I am 100% committed to Schalke and always have been since joining the club.

"I've loved every single minute of being a Schalke player and my love for the club, fans and team-mates will never go.

"I will always give everything I have when I represent the club to show how much I love Schalke 04."