The militant group Islamic State said it carried out an attack on a Shi'ite Muslim shrine in Iran on Wednesday which killed 15 people, escalating tensions in a country reeling from a wave of protests and prompting warnings of a response from Tehran, Reuters reports.
Iranian officials said they had arrested a gunman who carried out the attack at the Shah Cheragh shrine in the city of Shiraz. State media blamed "takfiri terrorists" - a label Tehran uses for hardline Sunni Muslim militants like Islamic State.
The group has claimed previous attacks in Iran, including deadly twin bombings in 2017 which targeted Iran's parliament and the tomb of the Islamic Republic's founder Ayatollah Ruhollah Khomeini.
Interior Minister Ahmad Vahidi blamed the protests sweeping Iran for paving the ground for the Shiraz attack, and President Ebrahim Raisi said Iran would respond, according to state media.
"Experience shows that Iran's enemies, after failing to create a split in the nation's united ranks, take revenge through violence and terror," said Raisi, speaking before Islamic State released its claim of responsibility.
"This crime 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 semi-official Tasnim news agency said the attacker shot an employee at the shrine entrance before his rifle jammed and he was chased by bystanders.
He managed to fix his gun and opened fire on his pursuers, before entering a courtyard and shooting worshippers. Several women and children were among the dead, it said.
A witness at Shah Cheragh told state television: "I heard sounds of gunfire after we prayed. We went to a room next to the shrine, this lowlife came and fired a barrage of shots. Then (the bullet) hit my arm and leg, it hit my wife's back, but thank God my child was not hit, he is seven years old."
