Washington - The U.S. Justice Department began proceedings Thursday to revoke the citizenship of a Ukrainian-born man who it said collaborated with the Nazis and helped liquidate a Jewish ghetto in Poland.

The request was made before a federal court in Detroit against Ivan "John" Kalymon, 82, of Troy, Michigan.

The official who announced the request, Christopher Wray, assistant attorney general in charge of the department's Criminal Division, said Kalymon was a member of a Nazi-operated Ukrainian Auxiliary Police unit in Lviv, a city now part of Ukraine, that rounded up Jews, imprisoned them in a ghetto, terrorized them, supervised their forced labor, killed those trying to escape and led survivors to extermination and forced labor camps.

The Justice Department said Nazi documents showed Kalymon participated on a daily basis in such persecution and admitted shooting Jews in a wartime report found by U.S. intelligence officers.

"John Kalymon has admitted his participation in Nazi mass murder," Wray said. "He must not be permitted to retain the privilege of American citizenship."

The department said Kalymon entered the United States in 1949 and lied about his Nazi past to become a U.S. citizen in 1955.

The United States does not allow people who participated in Nazi autrocities to obtain U.S. citizenship.

Since 1973, the United States have stripped 73 people of U.S. citizenship for participating in such abuses and have deported 59.