Ganz's strike, after the home goalkeeper Geert De Vlieger had fumbled an overhead kick by Marco Branca, cancelled out a 27th-minute goal by Bruno Versavel, who slammed a fierce half-volley from just outside the area past Gianluca Pagliuca following a Tibor Selymes cross from the left.
Ganz came close to a winner for Inter - trying to win the Uefa Cup for the third time in seven seasons - when he hit a post in the 88th minute. The Belgian club's coach, Johan Boskamp, said: "It isn't over yet."
In another first-leg tie, Germany's Schalke 04, trying to reach their first European semi-final since 1970, beat Valencia of Spain 2-0 in Gelsenkirchen. The defender Thomas Linke headed in a free-kick from Olaf Thon in the first half, and the Belgian striker Marc Wilmots added a late second goal.