Borussia Dortmund says central defender Mats Hummels has asked to be released from his contract so that he can move to Bundesliga rival Bayern Munich.

Hummels was on the Germany squad that won the 2014 World Cup in Brazil - scoring the winner against France in the quarterfinals - and is a key player for Dortmund, which is second in the Bundesliga behind Bayern.

He would be the third Dortmund star to leave for Bayern in recent seasons, after striker Robert Lewandowski and attacking midfielder Mario Goetze - scorer of Germany's winning goal against Argentina in the World Cup final two years ago.

The 27-year-old Hummels started his career with Bayern, playing mainly for the reserves, before joining Dortmund permanently in the 2009-10 season, following a loan spell.

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