Gunmen attacked a major Shi’ite holy site in the Iranian city of Shiraz on October 26, killing at least 13 people and wounding dozens, the IRNA state news agency said.
The attack took place as security forces clashed elsewhere in the country with protesters marking 40 days since the death of Mahsa Amini, a 22-year-old woman who died in police custody after being detained for allegedly improperly wearing a head scarf.
The attackers shot at pilgrims and staff at the entrance to the Shah Cheragh mosque, IRNA quoted witnesses as saying.
IRNA described the attackers as "takfiri terrorists," a label used by officials in predominantly Shi'ite Muslim Iran to describe to hard-line Sunni Islamist groups. Police arrested two attackers and were looking for the third.
But the local police chief later said a lone gunman had carried out the attack and had been captured.
Interior Minister Ahmad Vahidi said many people had been injured and the death toll could rise further. He blamed the protests sweeping Iran for paving the ground for such "terrorist attacks."
President Ebrahim Raisi said the attack "will definitely not go unanswered, and the security and law enforcement forces will teach a lesson to those who designed and carried out the attack."
The attack took place as thousands of Iranians descended on the cemetery where Amini is buried in defiance of the authorities' warnings as nationwide protests and strikes continued despite a bloody crackdown on women-led protests.
October 26 marks 40 days since Amini's death and the end of the traditional mourning period in Iran.
Amini died in police custody in Tehran on September 16 after being arrested three days earlier for "improperly" wearing a mandatory Islamic head scarf, or hijab.
Her death, which officials blamed on a heart attack, sparked a wave of anti-government protests in cities across the country met by authorities with a harsh crackdown that the Oslo-based group Iran Human Rights says has killed at least 215 people, including 27 children.
Young women and schoolgirls have been at the forefront of the protest wave, one of the largest Iran's ruling theocracy has been confronted with since the Islamic revolution of 1979.
On October 26, hundreds of men and women gathered at the Aichi cemetery in Saghez, Amini's home town in the western province of Kurdistan, despite threats from the security services, which blocked traffic at the entrance into the city, forcing people to walk to the cemetery.
Iran's semiofficial ISNA news agency said about 10,000 people gathered at the cemetery. It also said that the Internet had been cut off in Saghez amid clashes between security forces and mourners.
Hengaw, a Norway-based group that monitors rights violations in Iran's Kurdish regions, also said that security forces teargassed and fired on protesters who massed in the city.
"Security forces have shot tear gas and opened fire on people in Zindan Square, Saghez city," Hengaw tweeted without specifying whether there were any dead or wounded.
The claim could not be independently verified.
Videos shared earlier online purportedly showed the participants chanting, "Woman, life, freedom" and "Death to the dictator," in apparent reference to Supreme Leader Ayatollah Ali Khamenei.
Iranian workers and shopkeepers across the country also joined in nationwide protests on October 26.
"The cities of Sanandaj, Saghez, Divandarreh, Marivan, and Kamyaran are on widespread strike" in Kurdistan Province, Hengaw said on Twitter. The claim could not be independently verified.
The 1500tasvir social media channel said that there were strikes in a couple of cities, including Tehran, Rasht, Isfahan and Kerman but added that it was difficult to see evidence of them online as "the Internet connection is too slow."
1500tasvir said later on Twitter that a "brutal crackdown" had taken place against protesters in multiple locations in Tehran, including a gathering at the Tehran Medical Association.
"Armed regime forces, outnumbered by barehanded protesters, retreat while still shooting!" it said in a tweet accompanied by a video showing protesters and armed security forces in the streets.