Stem cell expert Hwang Woo-suk on Thursday admitted that his team last year used ova samples from two of its researchers.

In a highly-awaited news conference at Seoul National University, Hwang said he will resign from all of his official posts, including chairman of the World Stem Cell Hub, and focus on his research.

He apologized for his inaccurate response to the British journal Nature on how he obtained human eggs for his research, saying a staff member who donated eggs requested confidentiality.

Hwang also made an apology for using illegally traded ova, but said he discovered the fact late last month after news media broke the story.

He said he alone is responsible for the controversy, expressing regret over the involvement of Hanyang University and MizMedi Hospital.

He said he will strive to become an ethical scientist who will reward the public's support and the hope of patients stricken with incurable diseases.