Iran has said it will avenge the killing of Revolutionary Guards Colonel Sayad Khodai - a day after he was shot dead by two people on a motorcycle in a rare assassination in the capital of Tehran.
President Ebrahim Raisi said on Monday: "I have agreed for our security forces to seriously follow up on this matter and I have no doubt that revenge for the pure blood of our martyr will be taken."
Guards spokesman Ramazan Sharif said the colonel's death has reinforced the determination of the Guards to confront Iran's enemies.
"The martyrdom of Colonel Khodai strengthens the determination of the Revolutionary Guards to defend security, independence and national interests and to confront the enemies of the Iranian nation," he told the semi-official Mehr news agency.
"The thugs and terrorist groups affiliated with global oppression and Zionism will face consequences for their actions."
Colonel Khodai was "one of the defenders of the shrines", the semi-official Tasnim news agency reported, citing military personnel or advisers who Iran claims fight on its behalf to protect Shia sites in Iraq or Syria against groups such as Islamic State.
Two unidentified men on a motorbike reportedly shot at Colonel Khodai five times in a car - an unarmored budget SAIPA Pride - among the most affordable and common Iranian vehicles.
While there has been no claim of responsibility for the killing, the semi-official ISNA news agency reported that members of an Israeli intelligence service network had been discovered and arrested by the Guards.
His assassination comes amid uncertainty over the revival of Iran's 2015 nuclear deal with world powers after months of stalled talks.
Sanam Vakil, deputy head of the Middle East and North Africa programme at Chatham House, said the aim of the killing was to unsettle Tehran as tensions escalate with its arch-enemy Israel over Iran's nuclear programme.
"Should Israel be responsible for the attack, it is a reminder of Israel's growing reach and destabilising capacity inside Iran," said Mr Vakil.
Iran continues to deny accusations it is producing a bomb and claims its nuclear programme has peaceful purposes - denouncing the killings as acts of terrorism carried out by Western intelligence agencies and Mossad.
Meanwhile, the Israeli Prime Minister's Office, which oversees the intelligence agency Mossad, declined to comment on the recent events.
Since 2010 at least six Iranian scientists and academics have been attacked or killed in similar slayings - several of them by assailants riding motorcycles, in incidents believed to have targeted Iran's disputed nuclear programme.
Iran has accused Israel of carrying out the attacks spanning more than a decade.
Most recently, Iran accused Israel of the particularly high-tech killing of Mohsen Fakhrizadeh - the country's chief nuclear scientist that masterminded the Islamic Republic's disbanded military nuclear programme.
He was killed by a remote-controlled machine gun on a country road.
Israel has declined to comment on the claims.