Fakhrizadeh died in hospital due to injuries sustained during a shoot-out between his bodyguards and “armed terrorists” Friday afternoon, the statement said.

Later on Friday, Iran wrote in a letter to UN Secretary-General Antonio Guterres that there are serious indications of Israeli responsibility in the assassination and that it reserves the right to defend itself. Mr. Guterres urged restraint and the need to avoid any actions that could lead to an escalation of tensions in the region.

Iran's UN envoy, Majid Takht Ravanchi, urged the UN Security Council to strongly condemn this inhumane terrorist act and take necessary measures against its perpetrators. Mohammad Bagheri, chief of staff for the Iranian armed forces, warned of "severe revenge" against those behind the killing.

Former head of the US Central Intelligence Agency (CIA), John Brennan, said the killing of the scientist was a "criminal," suggesting Iranian leaders to wait for the return of responsible American leadership on the global stage.