The Los Angeles-based center tracked the suspects down during an operation launched in Romania in September 2003. The suspects - who were not identified - are alleged to have participated actively in the persecution and murder of Jews in several places in Romania during World War II.
The center sent letters outlining their protest to the country's top prosecutor, Ilie Botos, and to another prosecutor.
"It would be a mockery of the memory of the victims of the Holocaust in Romania if those responsible for their deaths were not held accountable due to the failure of the Romanian judicial system to bring them to trial," Efraim Zuroff, chief Nazi hunter for the Los Angeles-based group said in a statement faxed to The Associated Press.
There was no immediate comment from the Romanian authorities, but last year, when the center urged Romanian authorities to speed up investigations into the case, Botos said that investigations had revealed evidence to support the allegations in at least some of the cases.
Zuroff submitted the cases in February 2005. They allegedly include former members of the fascist Iron Guard, as well as Romanian Army personnel who committed crimes against Jews.
Before 1940, 760,000 Jews lived in Romania. An estimated 420,000 died after being deported to concentration camps by the country's pro-Nazi ruler Ion Antonescu and the Hungarian authorities who controlled parts of Romania during the war. There are about 6,000 Jews in Romania now.