Image copyright AP Image caption China's Huang Jeifu told the summit China was making progress in ending organ harvesting

The Vatican has defended its decision to invite China to a conference on organ trafficking despite its record of using executed inmates as organ donors.

The head of the Pontifical Academy of Sciences (PAS) admitted he did not know whether the practice was continuing but said he hoped to encourage change.

Human rights groups say China is still using executed prisoners as a source of organ transplants.

Beijing says forced organ harvesting ended in 2015.

But the group Doctors Against Forced Organ Harvesting (DAFOH) said China's participation was compromising the conference and the PAS should reject its claim as no independent inspection had taken place.

Image copyright AP Image caption Falun Gong followers say detainees are being killed for their organs

"Without accountability, there is no reason to trust the government of China's claim that forced organ harvesting of prisoners has come to an end," said Dr Torsten Trey.

'Mass killing of innocents'

Those killed so their organs can be sold for transplant mainly include members of the Falun Gong, an exercise-based spiritual movement that became popular before being banned as a cult in 1999, but also include Christians, ethnic Tibetans and Uighurs and other people who have been imprisoned for their beliefs, campaigners say.

China has a shortage of donors and a big black market in organs.

DAFOH wants Beijing to prove publicly that a 1980s law allowing organ harvesting has been abolished.

The group's criticism follows a report last year by the International Coalition to End Organ Pillaging in China (EOP), which said the Chinese Communist Party was behind the mass killing of innocent prisoners.

Image copyright AP Image caption Mr Sorondo said he did not know if illegal organ tranplants were continuing in China

The US House of Representatives has condemned forced organ harvesting and called for its end.

China's controversial reformer

However the director of China's transplant programme insisted progress was being made despite some violations taking place.

"In my governmental organisation there is zero tolerance," Dr Huang Jeifu said.

"However, China is a big country, with 1.3 billion people, so sure, definitely, there is some violation of the law. If there is some violation of the law it will be severely punished."

Image copyright Getty Images Image caption China outlawed Falun Gong in 1999 and began a crackdown on followers

Correspondents say Dr Huang is a controversial figure, credited by some with reforming a notoriously corrupt system but accused by others of being complicit in allowing it to continue.

The Vatican conference is a response to Pope Francis's efforts to crack down on trafficking in humans and organs.

Delegates have been told how desperate patients flock to countries where regulations are lax and organs can be cheaply bought, such as Egypt, India and Mexico, for everything from kidneys to corneas.

Image caption A shortage of transplant organs is fuelling a lucrative black market in poor countries

The conference aims to declare organ trafficking a crime against humanity.

It is taking place against a backdrop of warming ties between China and the Vatican.

They are believed to be close to a historic agreement governing the selection of bishops for 10m Chinese Roman Catholics.