TEHRAN - In a threat of retaliation against the planners and perpetrators of the brutal terrorist assault in Shiraz, Iran's military chief on Thursday declared national security, peace, lives and property of the people as red lines of the armed forces.

The Daesh has claimed responsibility for the terrorist attack on Shah Cheragh's shrine late on Wednesday. The attack took place shortly before evening prayers, when an assailant opened indiscriminate fire on pilgrims within the shrine before being injured and apprehended by security forces.

Major General Mohammad Bagheri, the Iranian armed forces chiefs of staff, said in a statement that security and intelligence forces will swiftly punish the "internal and foreign designers and perpetrators" of the heinous crime for their despicable deeds.

He continued by saying that the individuals responsible for the most recent wave of disturbance in the country as well as others who had been duped in the matter were "undoubtedly accomplices in this great crime."

The Iranian commander highlighted that "the cruel Hebrew-Arab-Western triangle" was behind the conception and implementation of the attack.

The extremist who carried out the attack was a foreign national, according to Nour News Agency, which is connected to Iran's top security body, though it did not specify which country.

Authorities in the area revealed CCTV footage that showed the terrorist entering the shrine after concealing an assault weapon in a bag and firing at worshippers who were attempting to run and shelter in hallways.

Up to 15 victims faced martyrdom, while scores more suffered injuries.

Major General Hossein Salami, chief Commander of the Islamic Revolution Guards Corps (IRGC), also condemned the "brutal crime and wicked conduct" in Shiraz and pledged revenge against those responsible.

He issued a severe warning to the perpetrators and sponsors of the heinous murder, declaring that the Iranian people will finally bring them to justice.

According to the IRGC chief, the terrorist attack proved that those who are "enemies of the dignity, strength, and progress of Islamic Iran" are willing to commit any crime to "achieve their malicious goals and wishes" and are prepared to kill and shed the blood of helpless men, women, and children even during prayers.