The latest gains followed reports that American Mark McCormack's IMG marketing agency was considering a bid for the FA Cup winners and Premier League champions.
IMG declined to comment on the United story, but said it was interested in increasing its involvement in football.
Earlier this year IMG lost out to sportswear company Adidas in a battle for control of former French football champions Olympique Marseille.
United's shares soared 45.5p to 559p, valuing the club at almost pounds 350m. The share price has virtually trebled since the start of the year. The latest run was triggered when the chief executive, Martin Edwards, who owns 17 per cent of the company, said last week that United's status as Britain's most profitable club made it a likely bid target.
The publishing group VCI made a pounds 300m bid for United earlier this year which was rejected. Potential income from pay-per-view deals is also helping to drive the share price higher.
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