Berlin - French authorities are hounding Franck Ribery over under-age sex allegations because of France's awful Soccer World Cup, the chairperson of the midfielder's German club Bayern Munich said on Thursday.

"I think the whole story is politically motivated because of France's poor performance in the World Cup. Ribery is being made a scapegoat," Karl-Heinz Rummenigge told the German daily Bild.

"We are very worried about the outcome of the case."

Ribery, 27, was hauled in for seven hours of questioning by Paris magistrates on Wednesday. He was charged with having sex with an under-age prostitute and then released.

Ribery's French international team-mate Karim Benzema, 22, was also detained for questioning and justice officials said he too was likely to face charges over his alleged relations with the same teenage call girl.

The magistrate's indictment is the first stage of a judicial investigation that could lead to a trial and, if convicted, Ribery and Benzema face three years in jail and a fine of 45 000 euros ($58 000).

Ribery has never denied having paid for sex with Zahia Dehar, now 18, but his lawyer told reporters that the player had had no idea in 2008 that she was under-age.

The married midfielder failed to score in France's ill-fated campaign in the World Cup in South Africa, won by Spain earlier this month. France, which took the title in 1998, were eliminated in the group stage.

He is a highly valued member of Bundesliga champions Bayern, although last season he was plagued with injury and was suspended for its Champions League final defeat to Inter Milan after a red card in the semi-final first leg.