Mahsa Amini, died after falling into a coma following her detention by Iran’s morality police, a dedicated unit that enforces strict dress codes for women, such as wearing the compulsory headscarf, media reports said.

Her brother, Kiarash Amini, said he was waiting outside the detention center on the day of her arrest when he heard screaming from inside. An ambulance arrived and a witness coming out of the center told him security forces had killed a young woman inside, according to local news media reports.

Ms. Amini was taken from the detention facility by ambulance to a hospital shortly after her arrest and went into a coma there but was kept on machines, the outlets reported.

Human rights activists who have spoken to the family said the police grabbed Amini and forced her inside a police vehicle, based on reports. Her brother, Kiarash, intervened however the police told him that they are taking his sister to the police station for one hour of “re-education.”

Ms. Amini’s death has sparked widespread outrage among many ordinary Iranians, as well as some officials, senior clerics, celebrities and athletes. Many have not only condemned the apparent violence against her but also called for an end to the practice of harassing and detaining women for not observing the hijab rules.

Protests erupted in several neighborhoods in Tehran on Friday after her death was declared, with crowds chanting “death to the dictator” and “death to Khamenei,” referring to Iran’s supreme leader Ayatollah Ali Khamenei, according to witnesses and videos posted on BBC Persian and social media.

Jake Sullivan, the U.S. national security adviser, said on Twitter that the United States was “deeply concerned” by the death of Ms. Amini, “who was reportedly beaten in custody by Iran’s morality police.”

Iran’s former vice president, Mohammad Ali Abtahi, said in a tweet that even the news of Ms. Amini’s stroke was enough to make several generations of Iranians hate religion and its teachings.

Ali Daei, an Iranian soccer legend and former captain of the national team, posted Ms. Amini’s picture on his Instagram page with the message, “What have you done to the country? My daughter asks what happened, what can I tell her?”

Over the decades, women have increasingly pushed back, particularly in the big cities, wearing their headscarves far back on their heads to reveal their hair.