Last year, Lithuania opened a criminal investigation against Yitzhak Arad, a former director of Yad Vashem, who survived the Holocaust in Lithuania and fought with local resistance fighters against the Nazis.

Lithuanian authorities officially asked Israel to allow it to investigate the 81-year-old Arad on suspicion that he took part in the murder of Lithuanian civilians during the Holocaust. The case is based on Arad's memoir, in which he describes his experiences as a partisan in Nazi-occupied Lithuania

In the letter, Yad Vashem chairman Avner Shalev charged that Lithuania was conducting historical revisionism and distortion that aimed to compare the partisan activity with the crimes of the Nazis and their collaborators.

"Destructive historical revisionism seems to be taking place in Lithuania regarding this case, by calling into question legitimate, previously lauded wartime combat in an obvious attempt to propagate unfounded beliefs and distort historical truths, he wrote in the letter," handed to Vaitiekunas on Wednesday.

It is clear that initiating criminal proceedings into Dr. Arad's involvement in Lithuanian partisan activity during World War II is tantamount to a call for an investigation into all partisan activity, he wrote. Any attempt to equate those actions with illegal activities, thereby defining them as criminal, is a dangerous perversion of the events that occurred in Lithuanian during the War.

No comment from Lithuanian officials was immediately available.

The Holocaust in Lithuania was unique in that it is believed that most of the Jews there were murdered by local citizens. The Order Police began killing Jews as soon as the Soviets left in 1941, and even before German troops arrived. Out of a prewar population of 220,000, only a few thousand Jews survived the war in Lithuania - representing the largest percentage of Jews murdered in one country during the Holocaust.

About 6 million Jews were killed by the Nazis and their collaborators in Europe during World War II.

haaretz.com