An Iranian police officer was stabbed to death during unrest near the capital Tehran, as protests over the rising cost of living entered their twelfth day.

According to the Fars News Agency, Shahin Dehghan, a police officer in the city of Malard west of Tehran, was killed hours earlier after being stabbed while “trying to contain the unrest” in the area. The agency added that efforts are under way to identify those responsible.

The protests began on December 28 following a strike by merchants in Tehran’s Grand Bazaar and have since spread to 25 of Iran’s 31 provinces. Demonstrations have been particularly concentrated in the western regions of the country, where Kurdish and Lur minority communities are largely based.