The teenagers also used a megaphone to shout anti-Semitic slurs during the attack Saturday, Hannover police spokesman Thorsten Schiewe said.
"I don't remember such a dramatic attack in Germany in recent times," said Michael Fuerst, the head of the Jewish community of the state of Lower Saxony.
Six suspects have been identified - five Arabic immigrants and one German - and police are looking for the other three, police said. The six range from nine to 19 years old and have been questioned by police.
Hannover prosecutors are investigating those involved on suspicion of incitement and causing serious bodily harm, prosecutor Irene Silinger said.
Stephan Kramer of the Central Council of Jews in Germany condemned the attack.
"This latest incident shows something we have not experienced before: A growing radicalization of young Muslims, which affects not only the Jewish community but the entire German community," Kramer told The Associated Press.
The Central Council of Muslims in Germany could not immediately be reached for comment.
Alla Volodarska of the Progressive Jewish community of Hannover dance group said its members were still in shock.
"What happened is just so awful," Volodarska told the AP. "The teenagers started throwing stones the moment our dance group was announced, even before they started dancing."
Volodarska did not attend the event but talked to several members of the eight-person dance group. She said one female dancer was injured in the leg by the stones.
"There were many kids throwing stones, many of them, but we don't know the exact number," she said, adding that the group had often performed Israeli dances at festivals and never experienced this kind of hostility before.
The festival took place in Sahlkamp, an immigrant neighborhood in Hannover.
Fuerst blamed city festival organizers for not calling the police right away.
"The organizers tried to de-escalate the situation themselves instead of calling the police. That's just plain stupid," Fuerst said, adding he was meeting Friday with the interior minister of Lower Saxony about the incident.
The Association of Jewish University Students in Germany said Thursday the number of anti-Semitic slurs and death threats against Jews in Germany had increased in recent weeks due to the May 31 Israeli commando raid on a Gaza aid flotilla that left nine activists dead.
Kramer agreed and noted that online threats especially had risen.
"The threats are mostly sent by e-mail or posted online on social networking sites like Facebook or MySpace," Kramer said.
