Detainees in China's prisons, including members of religious minorities, continue to be killed and their organs removed, an independent panel of lawyers and other experts said this week.

Evidence overwhelmingly shows forced organ harvesting in China over several years, said representatives of the China Tribunal, an international body created to investigate the reports of abuse against prisoners of conscience in China.

"Forced organ harvesting is of unmatched wickedness – on a death for death basis – with the killings by mass crimes committed in the last century," Sir Geoffrey Nice, who chaired the tribunal, said in a prepared statement.

Beijing has repeatedly rejected accusations that it forcibly removes organs from prisoners of conscience.

Tribunal investigators said they spent 12 months collecting evidence, work that included questioning more than 50 witnesses, experts, investigators and analysts in public hearings held in April and in December 2018. The tribunal also evaluated written submissions, investigative reports, and academic papers.

Investigators called hospitals in China and asked about transplants for patients, officials with the tribunal said. Investigators have been previously told followers of the Falun Gong spiritual movement were the source of some harvested organs. Falun Gong followers as well as Uighur, a Turkic Muslim population in western China, gave testimony of undergoing repeated medical testing in Chinese jails, tribune officials said.

For years international rights groups have criticized China's practice of using organs from executed prisoners. Medical and rights groups say prisoners cannot freely give their approval.

Chinese authorities announced in 2014 they would end the practice of removing organs from executed prisoners on Jan. 1, 2015, while also labeling claims of forced organ removals as being politically motivated. But as recently as 2016 pro-Beijing news media in Hong Kong, a territory belonging to China that forbids execution and is currently witnessing massive protests tied to Beijing's growing influence, reported that the practice of removing organs from executed prisoners had international support.

China imprisons the second-highest number of people, after the United States, a figure that international estimates place at more than 1.5 million . The organ transplant trade in China is estimated to annually be worth $1 billion, the tribunal said.

The Falun Gong is a spiritual movement outlawed in China and its followers accuse authorities on the mainland of extracting organs from its members. The movement began in the early 1990s in northeastern China, and its practice of combining meditation and slow-movement exercises with the ideals of restraint, compassion and honesty quickly attracted a large number of supporters.

By the late 1990s the ruling Communist Party saw the movement's large following as a security threat. Persecution of the group began in April 1999, after 10,000 Falun Gong supporters gathered near the government offices in Beijing to ask for legal recognition.

The China Tribunal was initiated by the International Coalition to End Transplant Abuse in China (ETAC) and its members, whom include legal and medical experts, as well as academics, ethicists, researchers and human rights advocates.