Stem cell pioneer Hwang Woo-suk has denied using illegally obtained human eggs for his experiments.

In the United States to attend a meeting on stem cell hub, Hwang told Yonhap News Agency that he received eggs from donors who wished to help his research on embryonic stem cells.

A controversy has broken out in South Korea over the illegal trading of human eggs. MizMedi Hospital director Roh Seong-il, who conducted stem cell research with Hwang, recently admitted to using illegally traded ovaries for artificial insemination.

Hwang said he has no knowledge of the incident but that human eggs used in his labs have ethnical and transparent sources.