The Scottish champions successfully fended off interest in the 25-year-old in the past, with Norwich City having a bid rejected on the final day of the January transfer window and Hull City being rebuffed in June.
Hooper arrived at Celtic Park from Scunthorpe for a fee around £2.4m in July 2010 and has scored 82 goals in 138 appearances.
Nottingham Forest were also in contact over a possible transfer though Hoops manager Neil Lennon had not given up hope of keeping his prolific marksman.
Hooper has been the club's leading marksman in all three of his Parkhead seasons but is in the final year of his contract and could leave for free in 12 months' time.
Kenya midfielder Victor Wanyama, 21, has already moved south, to the Premier League, to join Southampton in a deal involving a reported £12.5m transfer fee.