Poland's president led muted ceremonies Saturday marking the 40th anniversary of a communist-era anti-Semitic purge, and vowed to grant citizenship to the Jews who were stripped of it upon leaving the country. "All of those who left then, and were forced to give up their citizenship, will have their citizenship returned to them if they want it," President Lech Kaczynski said at Warsaw's Gdansk Train Station. A plaque marks the symbolic point from which an estimated 15,000 Jews - survivors of the Holocaust and their children - were driven from Poland by the country's communist regime. "I treat that as my contribution to rectifying those sad and shameful acts," Kaczynski said. On March 8, 1968, police and Communist Party worker-activists invaded Warsaw University's campus. They attacked students protesting the expulsion of two colleagues who had spoken out against the closure of a play.