China has banned the harvesting of transplant organs from executed prisoners, a senior official said, but international medical practitioners warn that inmates' body parts may simply be reclassified as "donations" instead.

High demand for organs in China and a chronic shortage of donations mean that death row inmates have been a key source for years, generating heated controversy.

Since the start of this year, authorities have demanded all hospitals stop using organs harvested from executed prisoners, Huang Jiefu, head of the China Organ Donation Committee, reaffirmed on the sidelines of annual legislative meetings underway in Beijing, according to reports.

"China's organ donation industry has entered a new stage of development in which voluntary donation will be the only source of organs," Huang, a former vice health minister, said in an interview with China Business News published Tuesday.

Yet experts have voiced scepticism about the pledge, arguing that organs will continue to be harvested from inmates but that they will now be classified as "donations".

In a letter to The Lancet, a group of five medical professionals from the United States, UK and Australia -- including the executive director of non-profit Doctors Against Forced Organ Harvesting -- wrote that "current statements from China have a disconcerting sense of deja vu".

"China has avoided the end of use of organs from executed prisoners for a long time, with failed promises dating back to 2008," the five wrote in a letter in this week's issue of the medical journal.

"Additionally, prisoners have been redefined as citizens with the right to donate their organs, but the practice has not stopped," they wrote.

In a separate letter, four specialists from the United States, Germany, and Canada called on China to open its system to international inspections.

"China still uses organs from executed prisoners," they wrote. "The only difference is that these organs are now categorised as voluntarily donated organs from citizens. This change would officially bypass international ethical guidelines, and the unethical practice might never end."

They pointed to an interview last year in which Huang told the Beijing Times that death-row prisoners are still citizens and thus "they also have the right to donate organs".

"We aren't opposed to death row prisoners voluntarily donating their organs. We aren't depriving them of the right to donate," Huang said in the interview, noting that organs obtained from inmates would be entered into China's national voluntary organ donation system.

China banned trading in human organs in 2007, but demand for transplants far exceeds supply in the country of 1.37 billion people, opening the door to forced donations and illegal sales.

Organ donations are not widespread as many Chinese believe they will be reincarnated after death and therefore feel the need to keep a complete body.