Israel must face a “severe punishment” for the assassination of a top Hamas official in Iran, according to a senior Islamic Revolutionary Guards Corps official, who aired the threat amid an internal debate and international effort to discourage the attack.

“There is no doubt that the blood of this noble martyr will have an impact on severe punishment of the Zionist regime at the hands of the Islamic Republic,” IRGC Brig. Gen. Esmail Qa’ani wrote in a letter to Yahya Sinwar, the Gaza-based mastermind of the Oct. 7 terrorist attack that sparked the war between Israel and Hamas. “The heroic struggle of your brothers in the Islamic resistance will intensify the effect of this punishment and lead to the elimination of this ominous phenomenon as soon as possible.”