Esmaeil Baghaei Hamaneh made the remarks in his address to the 44th regular session of the Human Rights Council on July 9, Mehr News Agency (MNA) reported.
"The assassination of Lt. Gen. Soleimani is an illegal act and a great crime that has endangered world peace and security," Hamaneh said.
He stressed that the operation for assassination of the commander of the IRGC's Quds Force in Baghdad was an act of "state terrorism" and “an immoral and dangerous act.”
"The US action not only is a violation of international law and the UN Charter, but it is also a violation of human rights law," Hamaneh said.
The diplomat added "The UN rapporteur's report on the assassination of the commander of Iran's Quds Force cannot be challenged."
Earlier in this session, UN Special Rapporteur on extrajudicial, summary or arbitrary executions Agnes Callamard called the assassination of Lt. Gen. Soleimani by US forces a violation of international law.
The United States has failed to provide sufficient evidence of an ongoing or imminent attack against its interests to justify the strike on Gen. Soleimani’s convoy as it left Baghdad airport, Callamard said.
The UN human rights investigator had said on July 6 that the US drone strike in Iraq that led to the assassination of Lt. Gen. Soleimani and nine other people represented a violation of international law.
The attack violated the UN Charter, Callamard wrote in a report calling for accountability for targeted killings by armed drones and for greater regulation of the weapons.
“The world is at a critical time and a possible tipping point when it comes to the use of drones. ... The Security Council is missing in action; the international community, willingly or not, stands largely silent,” Callamard said.
"But absent an actual imminent threat to life, the course of action taken by the US was unlawful,” Callamard wrote in her report.
On January 3, the US assassinated Lieutenant General Soleimani, along with Muhandis, the second-in-command of Iraq’s Popular Mobilization Units (PMU), and a group of their companions in Baghdad. The operation was conducted with the direct authorization of US President Donald Trump. The US Department of Defense took responsibility for the assassination.
Iran has issued an arrest warrant for Trump and 35 others over Lieutenant General Soleimani's assassination and has asked for Interpol’s help, Tehran prosecutor Ali Alqasimehr said on June 29.