SEATTLE — The Justice Department asked a federal court Tuesday to revoke the citizenship of an 86-year-old Seattle-area man, saying he served in a Nazi unit that slaughtered 17,000 Serbian civilians during World War II.

Peter Egner, a native of Yugoslavia, served as a guard and interpreter with the Nazi-controlled Security Police and Security Service in Belgrade from April 1941 to September 1943, according to a complaint filed in U.S. District Court in Seattle.

Egner did not divulge that information after he immigrated to the U.S. in 1960 and applied for citizenship, the complaint said. Instead, it said, he falsely claimed that he served as a rank-and-file infantry sergeant in the German army, and he was granted U.S. citizenship in 1966.

Reached by telephone at his home in a suburban retirement community called Silver Glen, Egner confirmed his identity to The Associated Press but said he was unaware of the complaint. Asked about his alleged service with the security police, he said: "I have no idea what you're talking about.I'm sorry. Bye."

The complaint said that during an interview with federal authorities in February 2007, Egner admitted that he guarded prisoners as they were being transferred to the concentration camp of Semlin and the execution site of Avala, both near Belgrade. He also reportedly admitted serving as an interpreter during the interrogation of political prisoners; the unit tortured or killed many such prisoners.

His lawyer, Robert Gibbs of Seattle, confirmed that Egner served on a low level in the security police when he was 19 or 20, but said his client denies participating in any persecution. The complaint did not allege that Egner himself tortured or killed anyone, and did not make reference to how many times he might have transported prisoners or interpreted during interrogations, Gibbs noted.

And, the lawyer argued, the U.S. has never taken the position that anyone who had anything to do with the Nazi war effort must be barred from the country.

"I don't think he was involved at the level that would allow them to take away his citizenship," Gibbs said. "He's been in the U.S. for almost 50 years now, and no one has anything bad to say about his time here."

The Justice Department, citing Nazi documents, said that in the fall of 1941, Egner's unit executed 11,164 people — mostly Serbian Jewish men, suspected communists and Gypsies — and that in early 1942, it murdered 6,280 Serbian Jewish women and children who had been prisoners at Semlin. Daily over the course of two months, those women and children were taken from the camp and forced into a specially designed van, in which they were gassed with carbon monoxide.

"No one who participated, as we allege the defendant did, in the diabolical Nazi program of persecution is entitled to retain U.S. citizenship," said Eli M. Rosenbaum, director of the Justice Department's Office of Special Investigations.

Rabbi Marvin Hier, founder and dean of Nazi watchdog the Simon Wiesenthal Center, said that the unit was a mobile killing squad made up of volunteers who joined because it brought them special rations like cigarettes, salami and liquor.

"They were professional killers who loved their jobs. They liquidated men, women and children," Hier said by telephone.

Egner "managed to escape and rewarded himself to the ripe old age of 86," Hier said. "He should be deported, tried for his crimes, and if convicted he should spend the rest of his life in jail. There should be no pity because of his age."

Since that office began trying in 1979 to track down former Nazis in the U.S., it has won cases against 107 people, and in recent years more than 180 people have been barred from entering the country because of past ties to the Nazis, the Justice Department said in a news release.

The Immigration and Nationality Act of 1952 provides for revocation of citizenship obtained through misrepresentation, and Egner's service with the Nazis is evidence of a lack of good moral character — a requirement for citizenship, the complaint said.