Disgraced cloning scientist Hwang Woo-suk went on trial Tuesday on charges of fraud and embezzlement in a scandal over faked stem cell research that undermined global hopes of dramatic new treatments for incurable diseases.

Hwang was indicted last month for allegedly accepting $2.1 million in private donations based on the outcome of the falsified research and embezzling about $831,000 in private and government research funds.

Hwang also was accused of buying human eggs for research, a violation of the country's bioethics law.

On the stand Tuesday, Hwang denied faking data for a key academic paper that was published in 2004 on his groundbreaking research.

"I was not involved in the process, I just received results," he said. "I fully trusted [my colleagues] without doubts, but it was clearly my mistake to approve the results."

If convicted, the 52-year-old scientist faces at least three years in prison. Hwang is being tried along with five colleagues who face similar charges.

The prosecution said in its opening statement that Hwang's deception was "a fraud case unmatched in history for the whole Korean people and the whole world."

"The people, as high as their expectations were, felt a great sense of loss and mental anguish," the prosecution said.

The next hearing in the trial was scheduled for July.

Hwang, who hasn't been seen in public since March, appeared nervous as he arrived at Seoul Central District Court. He would not speak with journalists.

"We'll protect you until the end!" supporters shouted.

They formed much of the courtroom audience as the proceedings got under way.

Hwang was once hailed as an international stem cell pioneer and national hero. But he was fired in March as a professor at Seoul National University's veterinary department amid allegations he fabricated data for two high-profile papers published in academic journals in 2004 and 2005.

He admitted inflating data but accused other researchers of deceiving him with falsified research results.

His claims of advances in embryonic stem cells, the basic human cells that can develop into nearly any kind of tissue, had offered hope of new treatments for millions of patients suffering from debilitating diseases such as Alzheimer's and Parkinson's.

Creating patient-specific stem cells with a patient's own DNA would be a key breakthrough because they theoretically could be used for treatments to replace sick cells that wouldn't be rejected by the body.

Hwang has insisted he has the technology to do what he claimed, and has apologized to the nation over the controversy.