US officials and world leaders remained silent on Friday night's assassination of Iran's top nuclear scientist, Mohsen Fakhrizadeh, while the UN called for restraint and the former CIA chief said the assassination was "highly reckless".
No immediate remarks were issued from the transition team of the White House, Pentagon, US State Department, CIA or US President-elect Joe Biden, report Times of Israel. Other countries' leaders were equally mum. Israel did not comment on the assassination and no party claimed responsibility.
John Brennan, the former head of the CIA, called the assassination a crime in the region that risked inflaming conflict. As Tehran pointed the finger at Israel, Brennan said he did not know who was to blame for the killing.
"This was a criminal act & highly reckless. It risks lethal retaliation & a new round of regional conflict," Brennan said in a series of tweets.
"I do not know whether a foreign government authorized or carried out the murder of Fakhrizadeh," he said. "Such an act of state-sponsored terrorism would be a flagrant violation of international law & encourage more governments to carry out lethal attacks against foreign officials."
Brennan noted that Fakhrizadeh was not a designated terrorist or a member of a terror group, which would have made him a legal target.
A strong critic of US President Donald Trump, Brennan urged Tehran to "resist the urge" to retaliate and "wait for the return of responsible American leadership on the global stage," referring to Biden, who will replace Trump in the White House on January 20.
US officials told CNN that they were closely watching the aftermath of the assassination, but refrained from publicly speaking because of concerns that the already volatile regional situation would be further stoked.
The US military is not preparing any action against Iran, and believes that Tehran will respond quickly to any missile strike attacks, according to the article, citing several US officials.
One American official told the network that the killing "would be a big deal" and that more information on the incident was being pursued by US intelligence.
In support of American troop withdrawals from Iraq and Afghanistan, the USS Nimitz aircraft carrier and other US warships are heading into the Persian Gulf, but the move was determined before Fakhrizadeh's assassination, a US defense official told CNN. Earlier this month, the USS Nimitz left the Gulf for Indian Ocean maritime exercises.
US Secretary of State Mike Pompeo announced on Friday evening that the US was sanctioning "four entities in China and Russia for their support of Iran's missile program, which remains a significant proliferation concern."
"We will continue to use all our sanctions tools to prevent Iran from advancing its missile capabilities," Pompeo said, without mentioning the killing of Fakhrizadeh.
Trump himself retweeted a posting from Israeli journalist Yossi Melman, an expert on the Israeli Mossad intelligence service, about the killing. Melman's tweet called the killing a "major psychological and professional blow for Iran."
US Senator Chris Murphy, the leading Democrat on the Senate's Middle East subcommittee, said, "If the primary purpose of the killing of Mr. Fakhrizadeh was to make it harder to restart the Iran nuclear agreement, then this assassination does not make America, Israel or the world safer."
"I have not yet been briefed on this incident, but: Every time America or an ally assassinates a foreign leader outside a declaration of war, we normalize the tactic as a tool of statecraft. The risk is that the security benefit can be very short lived," Murphy said on Twitter.
At the United Nations, Secretary-General Antonio Guterres called for restraint following the killing.
"We have noted the reports that an Iranian nuclear scientist has been assassinated near Tehran today. We urge restraint and the need to avoid any actions that could lead to an escalation of tensions in the region," his spokesman Farhan Haq said, according to Reuters.
Later on Friday, Iran sent a letter to Guterres and the UN Security Council alleging "serious indications of Israeli responsibility," Reuters reported.
"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 rights to take all necessary measures to defend its people and secure its interests," said Iran's UN envoy, Majid Takht Ravanchi.
The Hamas terror group said, "This assassination comes against the background of persistent American and Zionist threats against the Islamic Republic of Iran."
Fakhrizadeh was killed Friday in an ambush in Absard, a village just east of the capital Tehran, Iran's defense ministry said. The shadowy scientist was alleged to be the mastermind of Iran's rogue nuclear weapons program.
Several top Iranian officials indicated they believed Israel was behind the killing in the hours after the attack, with one adviser to the Islamic Republic's supreme leader vowing revenge.
The killing risks further raising tensions across the Mideast, nearly a year after Iran and the US stood on the brink of war after an American drone strike killed top Iranian general Qassem Soleimani in Baghdad.
It comes just as Biden stands poised to be inaugurated in January, and will likely complicate his efforts to return America to a pact aimed at ensuring Iran does not have enough highly enriched uranium to make a nuclear weapon.
Israel has long been suspected of carrying out a series of targeted killings of Iranian nuclear scientists nearly a decade ago, in a bid to curtail Iran's nuclear program. Israeli TV coverage noted that Friday's attack was far more complex than any of those previous incidents. Israel has never acknowledged assassinating people involved in the Iranian nuclear program.