File Photo: Abdolhamid Rigi. AFP
The province -- one of Iran's poorest -- is home to the ethnic Baluch minority and had been the site of often deadly violence even before nationwide protests erupted in September over the death in custody of 22-year-old Iranian Kurdish woman Mahsa Amini.
"Mowlavi Abdulvahid Rigi... was kidnapped Thursday by unknown assailants and died a martyr's death" in the town of Khash, the provincial security council said in a statement.
"An investigation has been opened" into the killing, it added.
The Islamic Republic has been gripped by demonstrations since the September 16 death of Amini, after her arrest by the morality police in Tehran for allegedly violating the country's strict dress code for women.
Iran's top security body, the Supreme National Security Council, said on December 3 that more than 200 people have been killed in the unrest.
Oslo-based non-governmental organization Iran Human Rights said on Wednesday that Iran's security forces had killed at least 458 people, including at least 128 in Sistan-Baluchistan.
The province's Baluchi minority, who adhere to Sunni Islam rather than the Shia branch predominant in Iran, have long complained of discrimination.