World leaders urge calm after assassination of Iran scientist Fakhrizadeh

Turkey slammed the killing of a leading Iranian nuclear scientist as "terrorism," as European leaders urged calm amid fears of rising tension.

Iran has vowed a "calculated response" to the assassination of Mohsen Fakhrizadeh on Friday, which it blamed on Israel after the country singled the scientist out for leading Iran's alleged attempts to develop a nuclear weapon. 

Turkey's foreign ministry said on Sunday it condemned "this heinous murder" and called for "all parties to act with common sense and restraint".

"Turkey is against all initiatives aimed at disrupting peace in the region and against all forms of terrorism, no matter who their perpetrator or target are," the ministry said. 

On Sunday, the United Arab Emirates, which has recently normalised ties with Israel, condemned the "heinous" killing of Fakhrizadeh, urging all parties to exercise restraint.

"The UAE condemns the assassination of Mohsen Fakhrizadeh and (calls) on all parties to exercise self-restraint to avoid dragging the region into new levels of instability and a threat to peace," the foreign ministry tweeted.

It described Fakhrizadeh's killing as an "heinous crime".

British Foreign Secretary Dominic Raab said the UK was waiting for more information but noted that international law was against the targeting of civilians. 

"We are concerned about the situation in Iran and the wider region. We do want to see de-escalation of tensions," Raab told Sky News on Sunday. 

'Calculated and decisive answer'

Germany's foreign ministry urged for extra restraint ahead of the coming change of administration in the United States, which is expected to see Joe Biden re-open nuclear talks with Iran after outgoing President Donald Trump tore up the previous agreement. 

Iran has suggested any response will not be immediate to avoid sparking a war, which it described as the "trap of the Zionist regime".

"Iran will give a calculated and decisive answer to the criminals who took Martyr Mohsen Fakhrizadeh from the Iranian nation," Kamal Kharrazi, a senior adviser to Ayatollah Ali Khamenei, said in a statement on Sunday.

I have no clue who did it. It's not that my lips are sealed because I'm being responsible. I really have no clue'

- Israeli cabinet minister Tzachi Hanegbi

The Syrian government, which was backed by Iran as it put down opposition protests and an ensuing civil war, echoed the accusations against Israel. 

Israeli cabinet minister Tzachi Hanegbi told the country's N12 news on Saturday: "I have no clue who did it. It's not that my lips are sealed because I'm being responsible. I really have no clue."

Israeli Prime Minister Benjamin Netanyahu named Fakhrizadeh, and warned "remember that name," when he focused on the scientist during a 2018 presentation in which he accused Iran of still trying to develop nuclear weapons, despite a deal with global powers. 

UN Secretary-General Antonio Guterres urged restraint to avoid an escalation of tensions, his spokesman said.

Iran's UN envoy, Majid Takht Ravanchi, said in a letter to Guterres that Tehran "reserves its rights to take all necessary measures" to defend itself. He also called on the UN Security Council to condemn the killing and take steps "against its perpetrators".