BEIRUT — An Iranian doctor who went public with reports of tortured protesters he treated at Tehran’s most feared detention facility dies, amid conflicting reports of a heart attack, a car accident or suicide — raising opposition accusations that the 26-year-old was killed.

Revelations that protesters detained in Iran’s postelection crackdown were tortured, some to death, were a deep embarrassment to the country’s clerical rulers. Dr. Ramin Pourandarjani was pressured to change the death certificate of one of the most well known victims and later spoke to a parliament commission investigating the abuse, opposition Web sites reported.