Despite a pledge to stop abuses by its security forces, the ruling Sunni minority in the tiny Persian Gulf kingdom of Bahrain is engaged in systematic and disproportionate use of tear gas on its restive Shiite majority, permitting police officers to routinely fire volleys at point-blank range at crowds and into homes and vehicles in Shiite neighborhoods, a leading rights group said in a report released on Wednesday.

The group, the Physicians for Human Rights, which has been highly critical of the Bahraini monarchy’s behavior since the Shiite protests inspired by the Arab Spring uprisings began there 18 months ago, called the policy on tear gas use unprecedented in the world, even among dictatorships where tear gas is a staple tool for crowd control.

Its report, based on dozens of interviews of victims in Bahrain and forensic evidence gathered there by the group’s investigators in April, said the Shiite populace’s abnormally prolonged exposure to the tear gas’s toxic components had already led to an alarming increase in miscarriages, respiratory ailments and other maladies.

It documented examples of grievous wounds suffered by civilians whose skulls and limbs had been struck by metal tear gas canisters blasted from a few feet away. The report also described instances in which people not engaged in protests were attacked with tear gas fired into their cars and through the windows or doors of their homes, including at least two cases in which residents died from complications from exposure to the gas because they were trapped in enclosed spaces.