Brigadier General Abbas Nilforoushan was killed in the Israeli strikes on Beirut on Friday in which Hezbollah chief Hassan Nasrallah also died.
"There is no doubt that this horrible crime committed by the Zionist regime (Israel) will not go unanswered," Foreign Minister Abbas Araqchi said in a statement addressed to the commander of the Islamic Revolutionary Guard Corps, Major General Hossein Salami.
Earlier on Sunday, the Speak of Iran's parliament said Iran-aligned armed groups would carry on confronting Israel with Tehran's help following the killing of Nasrallah, Iranian state media reported.
An alliance known as the Axis of Resistance, built up over decades with Iranian support, includes the Palestinian group Hamas, Hezbollah in Lebanon, Yemen's Houthis, and various Shi'ite Muslim armed groups in Iraq and Syria.
"We will not hesitate to go to any level in order to help the resistance," Speaker Mohammad Baqer Qalibaf said.
He also issued a warning to the United States.
"The US is complicit in all of these crimes and ... has to accept the repercussions," he said.
Iran's vice-president for strategic affairs, Mohammad Javad Zarif, when asked about Nasrallah's assassination, told state media on Sunday Iran would react at an appropriate time of its choosing against Israel.
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