Autonomous weapons systems should be banned or else a global arms race of mass-produced killer robots is “virtually inevitable,” according to hundreds of prominent scientists, robotics and artificial intelligence (AI) researchers and luminaries from related professions.

An open letter, released late Monday and signed by more than 1,000 leading scientists and academics — including inventor and entrepreneur Elon Musk, IBM Watson design leader Kathryn McElroy and theoretical physicist Stephen Hawking — said fully automated weapons systems that are able to make decisions to use lethal force without human authorization pose a major and immediate threat to humanity.

“Artificial Intelligence (AI) technology has reached a point where the deployment of such systems is — practically if not legally — feasible within years, not decades, and the stakes are high: autonomous weapons have been described as the third revolution in warfare, after gunpowder and nuclear arms,” the letter reads.

Unlike unmanned aerial vehicles, which require the use of human operators, or missile defense systems, which are programmed exclusively to respond defensively to missiles, automated weapons systems would bypass human decision-making to pick military targets.

Researchers say existing military technologies, including Israel's Iron Dome missile defense system, as well as a U.K. prototype for a self-flying plane called the Taranis, could evole in the near future to become fully autonomous killers.

While such weapons could spare human troops from ever stepping onto a battlefield, those who signed the open letter say these automated machines would lower the threshold for war and could even carry out genocide. “Autonomous weapons are ideal for tasks such as assassinations, destabilizing nations, subduing populations and selectively killing a particular ethnic group,” the letter reads.

Urging a global ban upon the use of autonomous weapons systems, the open letter said countries should immediately stop research on their development, which would make a international arms race “virtually inevitable,” a course that would make autonomous weapons the “Kalashnikovs of tomorrow.”

“Unlike nuclear weapons, they require no costly or hard-to-obtain raw materials, so they will become ubiquitous and cheap for all significant military powers to mass-produce,” the letter said. “It will only be a matter of time until they appear on the black market and in the hands of terrorists, dictators wishing to better control their populace, warlords wishing to perpetrate ethnic cleansing, etc.”

The call comes amid a burgeoning movement to address the potential concerns that autonomous weapons systems pose to humanity.

The United Nations began formally considering the issue during the yearly gathering of the Convention on Conventional Weapons in 2014, and again in 2015 agreed to continue talks on the systems, which are set to resume against in November.

The Campaign to Stop Killer Robots, a global coalition of nine leading nongovernmental organizations, was created in 2013 to press the international community to take immediate action on autonomous killing machines.

Human Rights Watch (HRW), one of that campaign's chief members, released a report in April calling for a ban on killer robots, saying their use created “serious moral and legal concerns.”

Autonomous killing machines, HRW argued in a statement released in April, could lead to legal “immunity for the U.S. military and its defense contractors,” presenting an “almost insurmountable hurdle to civil accountability.”

The HRW statement said arms manufacturers are now “immune from suit when they design a weapon in accordance with government specifications and without deliberately misleading the military.”

Bonnie Docherty, senior Arms Division researcher at HRW, said at the time that “a fully autonomous weapon could commit acts that would rise to the level of war crimes if a person carried them out, but victims would see no one punished for these crimes.”

A separate statement issued on May 2014 and signed by Nobel laureates including Archbishop Desmond Tutu, former South African President F.W. de Klerk, Iranian human rights activist Shirin Ebadi and former Polish President Lech Walesa said, "It is unconscionable that human beings are expanding research and development of lethal machines that would be able to kill people without human intervention.”

The statement added: “Lethal robots would completely and forever change the face of war.”