A group of over 100 doctors on Monday urged the Australian government to end its "refusal to act" in the case of Julian Assange and insist the British government release the WikiLeaks founder from prison so he can be safely sent to an Australian hospital before "it is too late."

In an open letter addressed to Foreign Minister Marise Payne, the doctors say that "the most fundamental human rights of an Australian citizen are being denied by the British government."

The international medical experts, who hail from countries including the United States, Australia, and the United Kingdom, called upon Payne to abide by his "undeniable legal obligation to protect your citizen against the abuse of his fundamental human rights, stemming from U.S. efforts to extradite Mr. Assange for journalism and publishing that exposed U.S. war crimes."

Assange has been in London's Belmarsh prison since April for skipping bail seven years ago when he first took refuge at the Ecuadorian Embassy in London. He's facing possible extradition to the United States for alleged violations of the Espionage Act. His time at the embassy and at Belmarsh had led to "medical neglect and fragile health," the doctors said, adding that Assange continues to suffer psychological torture at the London jail.

It's not the first time the medical group has sounded alarm on Assange's deteriorating health conditions.

In a letter sent last month to British Home Secretary Priti Patel and Shadow Home Secretary Diane Abbott, the group expressed "real concerns, on the evidence currently available, that Mr. Assange could die in prison." U.N. Special Rapporteur on Torture Nils Melzer has also accused the U.K. government of "outright contempt for Mr. Assange's rights and integrity." In May Melzer said Assange exhibited "all symptoms typical for prolonged exposure to psychological torture."

The doctors referenced Melzer's concerns as well as their letter to the U.K. authorities, saying that document fell on deaf ears.

In addendum to the new letter, the doctors wrote that Assange is essentially stuck waiting "helplessly for whatever the U.S government holds in store for him"—a situation "akin to keeping someone bound and gagged while their assailant stands by sharpening their knives."

"The Australian government has shamefully been complicit by its refusal to act, over many years. Should Mr. Assange die in a British prison, people will want to know what you, Minister, did to prevent his death."

Ongoing detention at Belmarsh, the group said, is "medically reckless at best and deliberately harmful at worst."

"We therefore urge you to insist upon the immediate transfer of Mr. Assange from Belmarsh Prison to an Australian university teaching hospital, on urgent medical grounds, so that he can receive the assessment and treatment that he requires," the doctors wrote. They added:

That we, as doctors, feel ethically compelled to hold governments to account on medical grounds speaks volumes about the gravity of the medical, ethical, and human rights travesties that are taking place. It is an extremely serious matter for an Australian citizen's survival to be endangered by a foreign government obstructing his human right to health. It is an even more serious matter for that citizen's own government to refuse to intervene, against historical precedent and numerous converging lines of medical advice.

Assange is set to face another case management hearing this week Westminster Magistrates' Court and full extradition hearing in February.