"Chelsea Football Club can confirm that John Obi Mikel has joined the club," read a statement on the club's official website on Saturday.

The 19-year-old Mikel has been at the centre of dispute between the two English sides and his original club Lyn Oslo after he signed an agreement with United before making a U-turn and claming that he was forced to put pen to paper.

Roman Abramovich's club will also pay four million pounds to Lyn Oslo. United and Lyn will receive half the payment in a year.

Mikel is Chelsea's fourth signing this season after landing Germany captain Michael Ballack, AC Milan second all-time scorer Andriy Shevchenko and Salomon Kalou from Feyenoord.