The German government said Friday it regrets plans by families of Israeli athletes killed at the 1972 Summer Olympics in Munich to boycott a 50-year anniversary ceremony next month and said it was prepared to continue talks on further compensation.

Eleven Israelis and a German police officer were killed after members of the militant Palestinian group Black September broke into the Olympic Village on Sept. 5, 1972. They took Israelis hostage, hoping to force the release of Palestinian prisoners held by Israel and two left-wing extremists in West German jails.

The victims’ families announced Thursday that they would not attend the memorial ceremony, underscoring ongoing friction between Germany and Israel. The two countries have built strong ties despite the enduring legacy of the Holocaust, in which German Nazis systematically killed 6 million Jews during World War II.

Relatives of the athletes have long accused Germany of failing to secure the Olympic Village, refusing Israeli help and botching the rescue operation in which the German police officer and five of the attackers died.... Read More: Associated Press