The 26-year-old Belgium defender, who last season led City to their first top-flight crown since 1968, was delighted to commit his long-term future to the club.
The new contract has been put at a reported £130,000-a-week, which would place the City captain some way below the club's top earners, Yaya Toure and Carlos Tevez, who earn in excess of £200,000 each week.
He told www.mcfc.co.uk: "For me if you are good somewhere then there is no reason to look elsewhere. Man City as a project is not just a project of the owners or the people employed by the club; it is also my project."
He added: "I have been here since the beginning and I have seen everything at the club change inside and out. I have the feeling that I have contributed to it too. It is good to know that I can be at City for another six years. It is a compliment that the club feels so highly of me."