The Islamic Revolution Guards Corps (IRGC) vowed on Wednesday that the Resistance Axis will make "Israel" pay a heavy price for its "criminal and cowardly" assassination of Hamas' Politburo chief martyr Ismail Haniyeh.

"The heinous crime committed by the Zionist regime in killing Ismail Haniyeh... will undoubtedly be met with a harsh and painful response from the powerful Resistance Front," the IRGC said in a statement.

Read more: Global condemnations for assassination of martyr Ismail Haniyeh

The guards corps added that the Israeli crimes, which defy international law, are attempts to conceal their failure after nine months of war on Gaza, resulting in the massacre of tens of thousands of innocent Palestinian women and children.

Earlier today, the IRGC announced the martyrdom of Haniyeh in a missile targeting his place of residence in Tehran.

The assassination occurred while Haniyeh was visiting the Iranian capital, Tehran, to attend the inauguration ceremony of the newly elected President Masoud Pezeshkian.

Hamas confirmed the martyrdom of one of its top leaders, noting that he was killed in a "treacherous Zionist airstrike."

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Iranian leader Sayyed Ali Khamenei stressed that retribution for Haniyeh's blood is "Iran's duty because he was martyred on our soil," adding that the Israeli entity "brought upon itself the most severe punishment."

Pezeshkian mourned the head of the Political Bureau of Hamas, saying, "Iran mourns its partner in sorrow and joy, the longtime and proud companion on the path of resistance."

"Yesterday, I raised the victorious hand of Hajj Ismail Haniyeh, the martyr of Al-Quds, and today I must [carry him] on my shoulder to bury him," he said.

The Iranian president pledged that the Islamic Republic will fiercely defend its honor and territorial integrity, ensuring that terrorist invaders deeply regret their cowardly actions.

The Islamic Republic of Iran announced a three-day mourning period.

Read more: Rajoub mourns Haniyeh: A crime that should motivate national unity