According to the Iranian state news agency IRNA 24 people, including a journalist, have been killed in a terrorist attack at a military parade in Iran, while 53 others have been injured.
Iran will respond "swiftly and decisively" to an attack on southwestern Iran, Iranian Foreign Minister Mohammad Javad Zarif said.
"Terrorists recruited, trained, armed & paid by a foreign regime have attacked Ahvaz," Javad Zarif tweeted. "Iran will respond swiftly and decisively in defense of Iranian lives."
According to the political deputy governor of Khuzestan Province, Ali Hossein Hosseinzadeh, "the blind and coward terrorist attack" claimed lives of 10 people, including a journalist, Tasnim News Agency reported.
A total of 21 others were injured, Hosseinzadeh said, noting that death toll was likely to rise as some of the victims were in critical condition.
The official confirmed that two militants, who attacked the military parade, had been killed by the security forces, while two others had been arrested.
Earlier in the day, the Tasnim News Agency reported that between eight and 10 IRGC personnel were killed in the attack, with seven others injured.
"Shooting began by several gunmen from behind the stand during the parade. There are several killed and injured," a correspondent told Iranian state television.
Two militants were reportedly killed by the security forces, while two others are still at large.
Iranian state news agency Tasnim has reported that Takfiri terrorists opened fire at people in the city of Ahvaz.
The shooting lasted 10 minutes and it came from a park near the parade. Attackers were wearing military uniforms, according to reports.
The military parade was held in honor of the anniversary of the beginning of an armed conflict between Iran and Iraq.
On June 7, 2017, a group of four people dressed in women's clothes opened fire in the Iranian Parliament, which was followed by an explosion. A separate terrorist attack targeted the Mausoleum of Ayatollah Khomeini.