President Ebrahim Raisi has said Iran will avenge the killing of a Revolutionary Guard colonel in Tehran.
Col Sayyad Khodai was killed outside his home on Sunday by gunmen on motorcycles, who opened fire on his car, state media said.
“I insist on the serious pursuit (of the killers) by security officials, and I have no doubt that the blood of this great martyr will be avenged,” Mr Raisi said.
“There is no doubt that the hand of global arrogance can be seen in this crime,” he said, using a term for US allies including Israel.
Mr Raisi was speaking just ahead of visiting Oman, where he was to meet Sultan Haitham.
Khodai's funeral was due to take place in Tehran at 5pm local time.
His killing was one of the most high-profile inside the country since the murder of nuclear scientist Mohsen Fakhrizadeh in November 2020.
Iran's Islamic Revolutionary Guard Corps described Khodai as a “defender of the sanctuary”, a term used for those who work on behalf of Iran in Syria or Iraq.
Iran maintains significant political influence in both countries. It has backed President Bashar Al Assad's regime in Syria's civil war.
State television noted that Khodai was “known” in Syria, where Iran has acknowledged sending in “military advisers”.
The official news agency IRNA said Khodai was killed by five bullets as he returned home at around 4pm on Sunday.
The agency published pictures showing a man slumped over in the driver's seat of a white car, with blood around the collar of his blue shirt and on his right arm. He was strapped in with his seat belt, and the front window on the passenger side had been shot out.
The Fars news agency reported that the state prosecutor had visited the scene of the killing and ordered the “quick identification and arrest of the authors of this criminal act”.
The guards said they had arrested several “thugs linked to the intelligence agency of the Zionist regime,” as Iran calls its enemy Israel.