With rumors that scientists are about to announce they have modified the genes of human eggs, sperm, or embryos, five prominent researchers on Thursday called on biologists to halt such experiments due to fears about safety and eugenics.

The call for a self-imposed research moratorium, which is extremely rare in science, was based on concerns that the work crosses an ethical line, said Edward Lanphier, president and chief executive officer of California-based Sangamo BioSciences Inc., senior author of the commentary published in the science journal Nature.

"Humans are not rats or other (experimental) organisms, and this is not something we want to do," Lanphier said in an interview. "The research should stop."