Araghchi's remarks came two days after the Friday strike on the Lebanese capital that killed General Abbas Nilforoushan, a top commander of the Quds Force, the Islamic Revolutionary Guard Corps foreign operations arm.

"This horrible crime of the aggressor Zionist regime will not go unanswered," the top diplomat said according to a foreign ministry statement.

"The diplomatic apparatus will also use all its political, diplomatic, legal and international capacities to pursue the criminals and their supporters," he added.

Iranian officials have strongly condemned the assassination of Hezbollah chief Nasrallah.

On Sunday, Iran's vice president for strategic affairs, Javad Zarif, said a response "will occur at the appropriate time and at Iran's choice, and decisions will definitely be made at the leadership level, at the highest level of the state," official news agency IRNA reported.

Iran's supreme leader Ayatollah Ali Khamenei has offered his condolences for Nasrallah's "martyrdom" and declared five days of public mourning.

Iranians on Sunday took to the streets of several cities across the country to express their anger at the killings of the Guards' Nilforoushan as well as Hezbollah's Nasrallah.

The secretary of Iran's Guardian Council, Ahmad Jannati, said Israel will "receive a forceful answer", threatening with "the destruction of the Zionist regime," according to Fars news agency.