SEOUL (Reuters) - Key parts of a landmark paper from South Korea's most renowned stem cell scientist were fabricated and the researcher is seeking to have the work withdrawn, a close collaborator told South Korean media on Thursday.

The daily newspaper Hankyoreh and three South Korean television networks quoted Roh Sung-il as saying that he, stem cell scientist Hwang Woo-suk and another co-author of the landmark 2005 Science paper on tailor-made stem cells had notified the journal they were withdrawing the paper.

"Professor Hwang admitted to fabrication," Roh said on MBC television. Roh, a hospital administrator and specialist in fertility studies, was referring to a meeting he said he had with Hwang earlier in the day.

Repeated attempts to reach Hwang and his other team members were not immediately successful. Reporters were gathered in sub-zero temperatures late at night at Seoul National University hospital to seek comment from Hwang or his team members.

Members of Hwang's team plan to hold a press conference on Friday morning, a team member said, adding he was not sure if Hwang would attend.

Another television network, KBS, quoted Roh as saying: "I agreed with Hwang to ask for it (the paper) to be withdrawn."

Roh told media nine of the 11 stem cell lines that were part of the tailored stem study paper were fabricated and the authenticity of the other two was questionable.

According to recent reports in South Korean media, some of the photographic images of the stem cells lines may have been manipulated to make it appear as if there were 11 separate lines.

An official at Science, a leading U.S. academic journal, said the publication had not yet been able to find any communication from Hwang.

"We cannot yet confirm these media reports," she said.

Hwang's research team has dismissed previous reports questioning his research and said its work was vetted by a rigorous system of peer review prior to publication

On Tuesday, a U.S. stem cell expert who lent his name and credibility to South Korean cloning pioneers asked that his name be removed from their landmark scientific paper.

Dr. Gerald Schatten of the University of Pittsburgh asked Science to take his name off a human cloning study published by Hwang and colleagues at Seoul National University.

Hwang is best known in scientific circles for cloning the first human embryos for research and the landmark study published earlier this year about developing tailored stem cells that could lead one day to cures for ailments such as severe spinal cord injuries.

Hwang's team also created the world's first cloned dog.

Hwang has been at the center of a media storm since November 24 when he apologized for two junior women researchers donating their eggs for his work and for not releasing information about the incident promptly.

The international scientific community frowns on donations by researchers because of possible coercion.

Hwang -- who has spent time in hospital himself in recent days for apparent exhaustion -- is considered a hero in South Korea for bringing the country to the forefront of stem cell and cloning studies.