Newcastle manager Eddie Howe says he is "aware of the criticisms" of the club's third kit for the 2022-23 season.
Photos, which BBC Sport understand to be legitimate, of the shirt have been shared widely on social media.
The green and white design has been criticised because of its similarities to the Saudi Arabia national team kit.
Last week, Amnesty International said Newcastle wearing the shirt would be "clear evidence" of sportswashing by the Saudi state.
Newcastle were taken over in October by a Saudi Arabian-backed consortium. The Premier League approved the takeover after receiving "legally binding assurances" that the Saudi state would not control the club.