Mohamed Zidan grabbed the crucial goal after 20 minutes.

The Egyptian swept home Tamas Hajnal's pass to move the visitors to within four points of league leaders Bayer Leverkusen.

Karlsruhe, though, have now not won in eight games - taking just one point from a possible 24 in the process - and remain in the relegation zone.

The hosts could have gone ahead in the eighth minute when Godfried Aduobe forced Dortmund keeper Roman Weidenfeller to tip his header over the bar.

But Dortmund, and Zidan in particular, soon began to assert their authority.

The former Hamburg man fired wide after a defensive error and was then shut out by keeper Markus Miller after being put through on goal.

Sebastian Freis volleyed into the side netting from a tight angle as Karlsruhe threatened briefly at the other end, but the lively Zidan was not out of the action for long.

Hajnal's low cross from the right picked him out in the centre of the area and he slotted the ball past Miller.

Hajnal almost created a second for Neven Subotic before the break, but Neven Subotic headed wide from his inswinging corner.

Karlsruhe, knowing even a point would move them out of the bottom three, came out fighting for the second half and Weidenfeller had to be alert to first save Antonio Da Silva's free-kick and a minute later Michael Mutzel's left-foot volley, which he fumbled but managed to keep out.

Dortmund might have settled the contest in the 58th minute, though, when Zidan dribbled half the length of the pitch before unselfishly cutting the ball back to the edge of the centre penalty area to Nuri Sahin, whose effort was parried by Miller.

The home side had a goal disallowed four minutes later when Edmond Kapllani found the net with a low finish only to be rightly flagged offside.

Miller again came to his side's rescue when he tipped Jakub Blaszczykowski's shot round a post, but his team-mates could not find the equaliser.