South Korean clone expert Hwang Woo-suk Friday said his team has technology to clone embryonic stem cells and had produced the cells in its research.

Hwang made the remarks at a press conference held at the Seoul National University.

However, at the televised news conference, the professor admitted some of the cloned embryonic stem cells in his research were "contaminated" and it was impossible to keep them alive.

Moreover, the 52-year-old professor also told reporters the pictures of the stem cells published along with his paper published in US journal of Science "had lethal error."

He said he will ask Science to retract of the paper after consultation with other some 20 co-authors.

He made apology to South Korean people for recent controversy surrounding his stem cell research and vowed to verify the authenticity of his research within 10 days.

In May this year, Hwang's team announced in a paper published in Science that it had successfully cloned 11 different stem cells tailored to individual patients, paving the way for future development of therapies for hard-to-cure diseases.

Hwang's news conference came one day after a co-author of Hwang's paper alleged Hwang fabricated partial images of the embryonic stem cells described in Hwang's paper.

Roh Sung-il, the administrator of Seoul's MizMedi Hospital, claimed on Thursday "Of the 11 alleged embryonic stem cells described in Hwang's study, nine are fake."

Roh's hospital had provided the human ova for Hwang's stem cell research.

Recently, local media quoted a former fellow researcher in Hwang's team as reporting that the 11 images of the stem cells published along with the paper in Science were copied and manipulated from two stem cells.

The new development of the controversy over Hwang's stem cell research came 20 days after Hwang admitted he used ova donated by his two female junior researchers in his research in 2003.

The action is widely viewed not comply to international ethical standard in bio-medical research.

Source: Xinhua