Constanta Mayor Radu Mazare expressed his regret to people who were offended by his dressing up as a Nazi officer. On Sunday evening, Mazare, 41, and his 15-year-old son performed on stage at the fashion show in Mamaia, a Black Sea resort town near Constanta, and both appeared to be dressed in Nazi uniforms.
He said the uniform was a reference to the film "Valkyrie," in which Tom Cruise plays Col. Claus Graf Schenk von Stauffenberg, the aristocratic army officer who was among those executed after a failed attempt to assassinate Adolf Hitler in July 1944.
Mazare's gesture attracted criticism in Romania and abroad.
A Romanian anti-discrimination group urged the general prosecutor's office to investigate. In Romania it is illegal to display swastikas and conviction can bring a three-year prison sentence.
The Simon Wiesenthal Center in Israel called on Mazare to apologize and resign.
Efraim Zuroff, the center's director, "expressed a sense of insult and outrage at the poor judgment Mazare exhibited."
"It would hard to adequately describe the depth of the pain that your appearance caused, not only to Jews and other victims of Nazism, but to any person of moral integrity who knows the history of World War II," the center said.
Mazare, 41, initially said that he had not seen the tiny swastika on his belt and downplayed his actions.
"I want to present my apologies to all those who were upset or offended by my appearance ... I said then that I do not share the Nazi ideology, on the contrary I appreciate those who wanted to assassinate the mad dictator," he said in his letter.
"I do not share or espouse nationalist, fascist or anti-Semitic ideas."
Mazare said he had been to Israel three times, and had visited the Dachau concentration camp to understand what the Jews suffered.
In the past, Mazare has dressed up and paraded in public as Latin American revolutionary Che Guevara and James Bond. Mazare, a member of the opposition Social Democracy Party, also was charged last year, along with 36 other government officials, with carrying out illegal real estate deals that cost the country 114 million euros ($143 million).
Romanian President Traian Basescu and Mazare are political rivals, and when Basescu was asked about the Nazi uniform during a news conference on Thursday, he criticized the mayor for "showing off in bad taste."
Romania denied participating in the Holocaust until 2004, when it accepted the findings of an international commission that Romanian authorities killed up to 380,000 Jews during World War II in territories under their control.