Dortmund boss Peter Bosz revealed Dembele missed training on Thursday and that the club could not get in contact him.
It emerged earlier today that Barcelona were closing in on an agreement with Dortmund and Dembele also missed training with the Bundesliga outfit, which pointed towards an imminent transfer.
Callum Bunce of Ladbrokes said: "Dembele couldn't have made his intentions any clearer with his recent actions, and the money suggests it's surely only a matter of time before the club let go of their prized asset".
"As there is no other offer from FC Barcelona to date, a transfer of the player to FC Barcelona is at present not more than likely".
He has been suspended until next week, Dortmund said.
'Dembele didn't show up for training today, ' Bosz told local reporters from Ruhr Nachrichten.
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Meanwhile, Dortmund manager Peter Bosz said France worldwide Dembele was absent from training on Thursday, per Ed Aarons of The Guardian, as speculation continues that the attacker will eventually move to the Camp Nou this summer.
Barcelona are eager to bring in at least one star quality signing following the sale of Neymar to Paris Saint-Germain, with Dembele, who enjoyed a fine first season with Dortmund, having emerged as one of the Catalan club's main targets.
"We want to have the best possible team". I have no idea why he wasn't there.
Precocious forward Dembele joined Dortmund last summer from French side Rennes for just 15 million euros.
Barcelona have been told they will have to pay £130m to secure the signing of Borussia Dortmund's Ousmane Dembele.