The foreign ministers of Germany, France and Italy have condemned what they say is a rise in anti-Semitism in their countries amid protests against the conflict in Gaza.

In a joint statement the ministers said that "anti-Semitic rhetoric and hostility against Jews, attacks on people of Jewish belief and synagogues have no place in our societies".

While the ministers say they respect freedom of speech, they say they will do everything possible to fight "acts and statements that cross the line to anti-Semitism, racism and xenophobia".

Since the outbreak of violence between Israel and Gaza, participants at anti-Israel demonstrations across Germany have frequently used anti-Semitic slogans and also called for Jews to be gassed.

In France, pro-Palestinian youths have clashed repeatedly with police, and on Sunday set fire to cars, pillaged stores and attacked two synagogues in the Paris suburbs.

Jewish groups have expressed shock and disgust about the growing anti-Semitism in Germany and other European countries with strong Muslim communities.

Berlin authorities this week banned pro-Gaza protesters from chanting an anti-Semitic slogan.

Police spokeswoman Cosima Pauluhn added Tuesday that police are investigating a sermon last week by a radical imam calling on worshippers at Berlin's Al-Nur mosque to murder Jews.