It was Ballack's 13th league goal of the season and it means Bayern need just eight points from the final four matches to retain their German title.

"Every goal is nice and I would not say this one was special," said Ballack. "My personal situation is not important. What is important is winning the German title and the cup."

German international captain Ballack broke the deadlock in the 69th minute and Mehmet Scholl added another for Bayern four minutes later.

It was a crucial victory for the reigning champions as SV Hamburg could have closed to within two points had Bayern only secured a point.

Hamburg swatted aside bottom side MSV Duisburg 2-0 to stay four points behind the league leaders.

Hamburg took the lead on 24 minutes with Duisburg defender Uwe Moherle scoring an unfortunate own goal.

Brazilian striker Ailton, on loan from Besiktas, made it 2-0 six minutes later slotting home after a brilliant defence-splitting pass from Sergei Barbarez.

Hamburg are now all but guaranteed one of the three Champions League spots with fourth-placed Schalke 04 now 11 points behind with four games left.

Schalke drew 1-1 with lowly FC Cologne on Saturday.

Bayern coach Felix Magath was celebrating his 600th Bundesliga game -- 306 as a player and 294 as a manager -- against Bielefeld but with 69 minutes gone it looked like being one to forget.

Bayern were struggling to find a way past the visitors but, as so often, Ballack came to their rescue with his low shot thumping off the post and back into the net off the goalkeeper.

After recent jeers from the home crowd -- unhappy that he is leaving on a free transfer at the end of the season -- Ballack was the toast of Munich and kissed the club badge for one of the last times.

While Ballack had a memorable afternoon his international teammate Oliver Kahn had a miserable one after injuring his eye in a freak training ground accident.

Kahn was left with a swollen black eye after a Michael Rensing shot crashed into his face.

Second choice goalkeeper Rensing started between the sticks in Kahn's place and kept a clean sheet.

Werder Bremen have been unable to keep clean sheets for most of this season and were left cursing another defensive lapse after a 1-1 draw with ten-man VfL Wolfsburg.

Wolfsburg had Argentine defender Facundo Quiroga sent off in the 26th minute for a late challenge on Miroslav Klose.

Paraguay international Nelson Haedo Valdez put Bremen ahead after six minutes but Marian Hristov levelled in the 23rd minute.

Bremen are now five points behind Hamburg who occupy the second automatic Champions League spot.