WARSAW - An apparent arson attack early yesterday devastated part of Warsaw's only synagogue, arousing shock in a city whose Jewish population was murdered by Poland's Nazi invaders.

Rabbi Michael Schudrich, head of the Ronald S. Lauder Foundation that sponsors programs to rebuild Jewish life and culture in Poland, said of the arson, "There are some elements in Poland who do not want to see democracy and pluralism blossom."

Two days before the fire an anonymous telephone caller to the Ronald S. Lauder Foundation, a Jewish educational charity represented by Rabbi Schudrich, had threatened "a bomb has been planted or will be planted very soon." Most of Poland's pre-1939 Jewish population was murdered by the Nazis. The synagogue stands only a few blocks from the site of the hellish Warsaw Ghetto.