WASHINGTON (Reuters) - The use of Taser stun weapons by U.S. police forces inflicts very few serious injuries, researchers said on Monday, but a leading human rights group was unswayed, pressing its call for a moratorium on them. The weapons, which are sometimes called stun guns and deliver an electric shock that incapacitates a person, are widely used by U.S. law enforcement. Those in this study were made Taser International Inc of Scottsdale, Arizona. Advocates argue these weapons allow police to subdue criminal suspects without resorting to more dangerous types of force, reducing injuries to officers and suspects. Critics say they are used too routinely and often against unarmed people who pose no threat, causing needless injuries and deaths. Researchers tracked police Taser use on 962 people in six jurisdictions around the country from July 2005 to June of this year. The study was funded by the U.S. Justice Department. Three of these people sustained moderate or severe nonfatal injuries requiring hospital admission, the study found. (3 out of 962 - compare that to an arm bar or baton) Two of them had head injuries suffered when they fell to the ground after being stunned. One had a type of muscle breakdown condition also seen in people whose body temperature gets too high, the researchers said. Of the rest, 216 people sustained mild injuries like abrasions, contusions and minor cuts requiring outpatient medical treatment, and 743 suffered no injury, the study found. Two who were shocked with the weapon died, but the researchers said investigations and autopsies determined the deaths to have been unrelated to the Taser. "The data that we've got supports the safety of these devices, in that 99.7 percent of the people on the receiving end in the real world had either no injury or mild injury," Dr. William Bozeman, an emergency medicine specialist at Wake Forest University School of Medicine in North Carolina who led the study, said in a telephone interview. 277 DEATHS Jared Feuer, who heads the U.S. southern regional office of Amnesty International, said the group has documented that 277 people in the United States have died after being shocked by a Taser since June 2001. "We do believe that there is a risk to the public safety, and we still call for there to be a moratorium on the use of Tasers" by police, Feuer said in an telephone interview. "Our concern is that Tasers interfere with a basic equation, which is that force must always be proportional to the threat," Feuer said, noting that about 80 percent of the people on whom a Taser is used by U.S. police are unarmed. "They are being used in a situation where a firearm or even a baton would never be justified," Feuer added. Bozeman said this was the first study to document the frequency and severity of injuries caused by the devices in real-life conditions, with doctors in the law enforcement agencies assessing each case. TASER International spokesman Steve Tuttle said of the study, "It confirms what we've been telling the public since day one -- that the Taser technology is a safer alterative for use of force for law enforcement." "There is nothing risk-free during a law enforcement encounter with use of force," Tuttle added, saying the study showed the devices are a "safer alternative" to injuries that might result from a nightstick or police dog bite. The findings were being presented at the American College of Emergency Physicians' Research Forum in Seattle.