Artur Wichniarek put the visitors ahead in the 19th minute. Leverkusen answered on the half-hour mark through Sergej Barbarez, but Jonas Kamper struck the winner for Bielefeld with seven minutes left.

Michael Skibbe's Leverkusen side have now lost four of their last five games, dropping behind Nurnberg on goal difference as they battle for the final UEFA Cup spot.

For Bielefeld, this was a third straight win and should ensure they have staved off any lingering relegation worries as they now have a six-point advantage over Alemannia Aachen.

Bielefeld had an early chance through a mistake from Leverkusen defender Karim Haggui, who slipped when chasing down a long ball, leaving Christian Eigler to poke it past goalkeeper Rene Alder. However, just as he was preparing to celebrate, the ball bounced back off the left-hand post and bounced to safety.

At the other end, Bielefeld defender Robert Tesche was lucky to avoid an own goal when he attempted to head the ball back to goalkeeper Mathias Hain only to see the ball go over the bar and onto the roof of the net.

However, it was Bielefeld who took the lead as they capitalised on another error. Full-back Marko Babic failed to close down Tesche who burst past him on the wing before crossing to Wichniarek who blasted the ball home.

Leverkusen drew level on the half-hour mark when Simon Rolfes' shot deflected off Bielefeld defender Tobias Rau, and Barbarez was on hand to fire the rebound home.

Both sides enjoyed good chances in the 54th minute. Wichniarek sent a header straight at Adler from a free-kick before Andriy Voronin failed to connect cleanly with Gonzalo Castro's cross as the ball went just wide left of Hain's goal.

But just when it began to look like honours would be shared, Kamper hit his side's second with a 30-yard screamer in the 83rd minute.