The 29-year-old had already said he was leaving Bayern but Chelsea had not previously admitted a deal was done.

    Jose Mourinho said: "I'm happy and very proud. I'm happy with the conversation I had with him and that's the reason he decided to come here."

    Chelsea, who have also been linked with forwards Andriy Shevchenko and Samuel Eto'o, have said they want to sign three new players this summer.

    Ballack, who led Bayern to three Bundesliga championships and three German Cups in his four years in Munich, was jeered by fans in his final appearance for the club against Borussia Dortmund.

    The midfielder scored Bayern's third goal in the 3-3 draw.

    After the game he blamed the club's management for manipulating public sentiment against him after he said he wanted to move to Chelsea next season.

    "Those things got whipped up a bit in recent weeks after some remarks by the club's management," Ballack told Premiere television.

    "The fans are sensitive to what is said. But I always tried hard to do my job and that should be honoured.

    "I want a new challenge now. I've got to accept some jeering. It shows I was an important player but it does hurt." Enditem