In a written statement as well as a televised speech on Saturday, the Iranian President Hassan Rouhani alleged that the Trump administration and Israel were behind the assassination of Iran's top nuclear scientist and operator Mohsen Fakhrizadeh near Tehran on Friday.

The assassination of Fakhrizadeh at the "dirty hands of the global arrogance, with the usurper Zionist regime working as its mercenary was the resulted from the frustration of Iran's sworn enemies,” he said in his written statement. ‘Global arrogance’ in the jargon of Iranian officials refers to the United States.

Iran’s Supreme Leader Ali Khamenei also released a short statement Saturday, praising Fakhrizadeh’s contributions and asking officials to quickly identify and punish the perpetrators and those who ordered his killing.

Later, speaking at a televised meeting of the National Coronavirus Combat Taskforce, Rouhani once again pointed a finger at the Trump administration and Israel and said Iran will "surely respond" to the killing of its scientist "at the proper time".

Mohsen Fakhrizadeh in an undated photo.

"The Iranian nation is smarter and cleverer than falling into the trap of Zionists. They are trying to create trouble and chaos but they should know that we are aware of what they are trying to do," he declared. Also referring to the outgoing Trump administration Rouhani said: "Our enemies are experiencing some very anxiety-filled weeks. They feel their pressure is dwindling and the international atmosphere is changing. For them it is very important to make the most of [their time] during these few weeks."

The Trump administrations, which pulled out of the 2015 nuclear agreement with Iran has been conducting a ‘maximum pressure’ campaign against Iran, imposing more and more sanctions on its troubled economy.

Analysts appearing on international media have argued that the killing perhaps aims to force Iran to retaliate, reducing chances of a rapprochement between the incoming Biden administration and Tehran.

The Iranian envoy to the United Nations, Majid Takht-Ravanchi, in a letter to Secretary-General Antonio Gutteres and the Security Council on Friday evening called the killing of Fakhrizadeh a "state-sponsored assassination and blatant violation of international law" with "serious indications of Israeli responsibility." The letter also alleged that the assassination was "another desperate attempt to wreak havoc" in the region.

“Warning against any adventuristic measures by the United States and Israel against my country, particularly during the remaining period of the current administration of the United States in office, the Islamic Republic of Iran reserves its right to take all necessary measures to defend its people and secure its interests,” the letter said and urged the Secretary-General and the Security Council to "strongly condemn the terrorist act and take necessary measures against its perpetrators."

The UN x Special Rapporteur on Extra-Judicial Executions Agnes Callamard on Friday in a tweet said there were many questions as to the circumstances of Fakhrizadeh's killing. "No State or non-State actors had yet claimed responsibility. But to recall: An extraterritorial targeted killing, outside an armed conflict is a violation of international human rights law prohibiting the arbitrary deprivation of life and a violation of the UN Charter prohibiting the use of force extraterritorially in times of peace," she explained in her tweet.