Global powers warned Friday that the American airstrike responsible for killing Iran's top general made the world more dangerous and that escalation could set the entire Mideast aflame.
Some US allies suggested Iran shared in the blame by provoking the attack.
The deaths of General Qassem Soleimani and associates drew immediate cries for revenge from Tehran and a chorus of appeals from other countries for reduced tensions between Iran and the United States. As US Secretary of State Mike Pompeo called world capitals to defend the attack, diplomats scrambled to chart a way forward.
"A further escalation that sets the whole region on fire needs to be prevented," German Foreign Minister Heiko Maas said. He said he told Pompeo that the strike had not "made it easier to reduce tensions." But Maas also noted that the assault "followed a series of dangerous Iranian provocations."
The White House justified the killings with a tweet alleging that Soleimani "was actively developing plans to attack American diplomats and service members in Iraq and throughout the region." The 62-year-old led Iran's elite Quds Force, which undertakes the country's foreign campaigns. Iranian state TV reported that 10 people were killed in the airstrike near Baghdad's airport.
"He should have been taken out many years ago!" US President Donald Trump tweeted.
Oil prices surged as investors fretted about Mideast stability. Saudi Arabia, Iran's top rival in the region, urged restraint and called on the international community "to ensure the stability of such a vital region to the entire world."
Social media flooded with alarm. Twitter users morbidly turned "WWIII" into the top trending term worldwide.
"We are waking up in a more dangerous world. Military escalation is always dangerous," France's deputy minister for foreign affairs, Amelie de Montchalin, told RTL radio.
Russia characterised the killings as "fraught with serious consequences." Foreign Ministry spokeswoman Maria Zakharova suggested that Trump ordered the strike with one eye on his re-election campaign.
"The US military were acting on orders of US politicians. Everyone should remember and understand that US politicians have their interests, considering that this year is an election year," Zakharova said in a TV interview.
His election opponents characterised Trump as reckless. Democratic presidential candidate Joe Biden said the president "tossed a stick of dynamite into a tinderbox."
China described itself as "highly concerned" and urged all parties "especially the United States, to maintain calm and restraint and avoid further escalation of tensions."
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US allies Britain, Germany and Canada suggested that Iran bore some responsibility for the confrontation.
German government spokeswoman Ulrike Demmer described the strike as "a reaction to a whole series of military provocations." She pointed to attacks on tankers and a Saudi oil facility, among other events.
"We are at a dangerous escalation point," she said.
The British foreign secretary, Dominic Raab, said his government had "always recognised the aggressive threat posed by the Iranian Quds force."
Following Soleimani's death, "we urge all parties to de-escalate," he said. "Further conflict is in none of our interests."
Canadian Foreign Minister Francois-Philippe Champagne said Soleimani's "aggressive actions have had a destabilising effect in the region and beyond."
There were warnings the killing could set back efforts to stamp out remnants of the Islamic State group.
A top European Union official, Charles Michel, said "the risk is a generalized flare-up of violence in the whole region and the rise of obscure forces of terrorism that thrive at times of religious and nationalist tensions."
Italy also warned that increased tensions "risk being fertile terrain for terrorism and violent extremism." But right-wing Italian opposition leader Matteo Salvini praised Trump for eliminating "one of the most dangerous and pitiless men in the world, an Islamic terrorist, an enemy of the West, of Israel, of rights and of freedoms."
Trump also won the support of Israeli Prime Minister Benjamin Netanyahu "for acting swiftly, forcefully and decisively."
In his calls to explain the strike to world leaders, Pompeo said the US is committed to bringing down tensions that have soared since Iranian-backed militia killed an American contractor and the US responded with strikes on the militia. That set off violent pro-Iran protests outside the US Embassy in Baghdad, which in turn set the stage for the killing of Soleimani.
"Doing nothing in this region shows weakness. It emboldens Iran," Pompeo said. "We don't seek war with Iran, but we at the same time are not going to stand by and watch the Iranians escalate."
In the Mideast, the strike provoked waves of fury and fears of worse to come.
Iraq's most powerful Shiite religious leader, Grand Ayatollah Ali al-Sistani, said in a speech during Friday prayers that the country must brace for "very difficult times."
In Iran, a hard-line adviser to the country's supreme leader who led prayers in Tehran likened US troops in Iraq to "insidious beasts" and said they should be swept from the region.
"I am telling Americans, especially Trump, we will take a revenge that will change their daylight into to a nighttime darkness," said the cleric, Ayatollah Ahmad Khatami.