Borussia Dortmund says Poland midfielder Jakub Blaszczykowski has extended his contract for three years and is now bound to the Bundesliga champion until 2016.

Blaszczykowski was one of the key players for Dortmund that won the second consecutive championship last season.

Dortmund has lost midfielder Shinji Kagawa to Manchester United but has retained most of the winning squad. It added Germany forward Marco Reus.

The club is still trying to persuade Poland striker Robert Lewandowski to extend his contract early. Lewandowski scored 22 goals last season.