German police say a set of crosses commemorating people who died trying to cross the Berlin Wall has been stolen, days before the 25th anniversary of the barrier's fall.

Police were alerted early Monday that the seven white crosses on the Spree riverbank, near the Reichstag parliament building in central Berlin, had gone missing. Similar crosses stand at several points along the former border.

A group calling itself the Center for Political Beauty claimed it was behind the crosses' disappearance. It said it wants to draw attention to the plight of refugees trying to get across modern Europe's external borders.

At least 136 people died between 1961 and 1989 trying to cross the wall that divided communist-run East Berlin from West Berlin. The wall fell on Nov. 9, 1989.