The Nigeria international has carried on from last season's superb campaign by scoring 11 goals in 14 games for his Belgian club. Last term, Onuachu scored 35 goals.
Berta has the striker under consideration for the January market, reports Marca.
Genk are willing to do business for €20m for the 27 year-old.
Onuachu joined Genk in 2019 for €6m.
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