The 21-year-old Dutch international, who joined Twente in 2009 after coming through Graafschap Doetinchem's youth system, was reported in the media to have moved for a 15 million euro (£11.7m) transfer fee.
De Jong scored 25 goals in 31 Eredivisie appearances last season in a breakout third season at the Enschede club.
His older brother, Siem, plays for Ajax.

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