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An airstrike north of Baghdad early Saturday local time hit two cars carrying members of an Iran-backed militia, according to an Iraqi official. At last five people were killed.

U.S. President Donald Trump says Maj.-Gen. Qassem Soleimani, killed in an airstrike, was planning imminent attack on U.S. diplomats and service members.

Iran says it's decided how to respond to killing of Soleimani, but mum on details.

U.S. is sending nearly 3,000 additional troops to Middle East as a precaution, officials say.

Price of oil surges after Soleimani's killing over fears of Iranian reprisals.

Canada's foreign affairs minister calls on all sides to 'pursue de-escalation.'

The late Iranian Maj.-Gen. Qassem Soleimani's "reign of terror is over," U.S. President Donald Trump said in a brief statement Friday, a day after the airstrike he ordered killed Iran's top general near Baghdad's airport.

In a prepared statement to media at his Mar-a-Lago resort before travelling to a rally, Trump reiterated what other U.S. officials have said of Soleimani: that he was planning "sinister attacks" on U.S. diplomats and service members.

"We caught him in the act and terminated him," Trump said.

Soleimani "made the death of innocent people his sick passion, contributing to terror plots as far away as New Delhi and London," he went on.

"We take comfort knowing that his reign of terror is over."

U.S. President Donald Trump says the targeted killing of an Iranian military commander, Gen. Qassem Soleimani, was not an act of war, but a way to prevent it. Trump insists the United States is not seeking regime change, but warns Iran's leadership that the future belongs to the Iranian people. 4:19

The U.S. is not seeking regime change in Iran, Trump said.

"We took action last night to stop a war," he said. "We did not take action to start a war."

Later Friday, Army Gen. Mark Milley, chairman of the joint chiefs of staff, said the U.S. had "compelling, clear, unambiguous intelligence" that Soleimani was plotting violent acts.

"Oh, by the way, it might still happen," Milley said, referring to the planned attacks.

Neither Trump nor Milley shared what evidence they had of imminent strikes against American assets.

Sen. Chris Murphy, Democract of Connecticut, fired off a number of tweets Friday questioning why the president did not seek Congress's approval for the airstrike.

"Soleimani was an enemy of the United States. That's not a question," Murphy tweeted. "The question is this — as reports suggest, did America just assassinate, without any congressional authorization, the second most powerful person in Iran, knowingly setting off a potential massive regional war?"

He also questioned the claims that the strike was meant to prevent attacks on Americans.

Here’s the thing - even if there was an “imminent attack”, it’s insane to argue that gives the President legal carte blanche to take any and all military actions. <br><br>The action needs to be tailored to stop the imminent harm. There is no evidence this was. —@ChrisMurphyCT

Murphy called on Congress to "force [Trump] into compliance" with the War Powers Act, which requires that the president seek congressional approval to enter an armed conflict.

Meanwhile, violence continued in Baghdad. In the early morning hours of Saturday, another airstrike north of the city hit two cars carrying members of an Iran-backed militia. At least five people were killed, according to an Iraqi official.

Iran vows 'harsh retaliation'

Earlier Friday, Iran's Supreme Leader Ayatollah Ali Khamenei warned that a "harsh retaliation is waiting" for the United States after Trump ordered the airstrike, which Iran state media reported killed 10 people.

Iran's Supreme National Security Council said Friday it has reached a decision, but isn't saying what it is, on how to respond to the U.S. killing of Soleimani, head of Iran's elite Quds Force and architect of its interventions across the Middle East.

The U.S. killing of Iranian Maj.-Gen. Soleimani, pictured in 2016, has stoked fears that tensions in Middle East could escalate drastically. (Ebrahim Noroozi/The Associated Press)

Calling Soleimani the "international face of resistance," Khamenei also declared three days of public mourning for the general's death.

The targeted killing marked a major escalation in the standoff between Washington and Iran, which has careened from one crisis to another since Trump withdrew from the 2015 nuclear deal and imposed crippling sanctions.

"This is different than the killing of Osama bin Laden and Abu Bakr al-Baghdadi," Kamran Bokhari, founding director of the U.S.-based Center for Global Policy, told CBC News on Friday.

"Baghdadi and Osama bin Laden were leaders of terrorist organizations. This is an official of the Iranian government, the Iranian military, someone ... whose myth and whose, you know, personality was groomed and developed by the Iranians for information operations purposes."

Watch as an expert discusses the impact of Soleimani's killing:

The killing of Iranian Gen. Qassem Soleimani by a U.S. airstrike will inflame tensions but likely won't trigger an all-out war in the Middle East, according to Kamran Bokhari, the founding director of the U.S.-based Center for Global Policy. 11:50

However, Bokhari doesn't think Soleimani's death will lead to a "doomsday scenario."

"The Iranians don't do conventional wars. They do asymmetrical warfare, and this is something that's already been happening," he said, referring to recent attacks on oil tankers in the Persian Gulf and Arabian Sea, and rocket attacks on Iraqi bases that housed U.S. personnel.

"So now, the question is what can they do — it will be tit-for-tat, but the idea that this will somehow lead to a major war in the Middle East that will spiral out of control, I don't think that's what the Iranians want."

The price of oil surged Friday on concerns Iran might respond to the killing by disrupting global supplies of energy from the Middle East. About 20 per cent of oil traded worldwide goes through the Strait of Hormuz.

The latest from the U.S.

The U.S. is sending nearly 3,000 additional troops to the Middle East as a precaution amid rising threats to U.S. forces in the region, U.S. officials said on Friday. Around 5,200 U.S. troops are based in Iraq, where they mainly train Iraqi forces and help to combat ISIS.

Also Friday, the Pentagon placed an Army brigade in Italy on alert to fly into Lebanon if needed to protect the American Embassy there. Speaking on condition of anonymity, an official said the U.S. could send 130 to more than 700 troops to Beirut from Italy. The official was not authorized to be identified.

Trump, who was vacationing on his estate in Palm Beach, Fla., and sent out a tweet of an American flag shortly after the attack, tweeted on Friday that Soleimani was planning to kill more Americans and "should have been taken out many years ago."

The U.S. Defence Department said it killed the 62-year-old Soleimani because he "was actively developing plans to attack American diplomats and service members in Iraq and throughout the region." It also accused Soleimani of approving the orchestrated violent protests at the U.S. Embassy in Baghdad.

Brian Hook, the U.S. special representative for Iran, told Dubai-based Al Arabiya TV that Soleimani was planning an imminent attack on U.S. facilities and workers in Iraq, Lebanon, Syria and other countries — and that the attack was going to kill hundreds of Americans.

Iraqi counter-terrorism forces stand guard in front of the U.S. Embassy in Baghdad. (Ahmad al-Rubaye/AFP via Getty Images)

U.S. Senate Republican leader Mitch McConnell said the Trump administration would brief congressional staff on Friday about the U.S. military strike against Soleimani and that it would likely conduct a classified briefing for all senators early next week.

"This terrorist mastermind was not just a threat to the United States and Israel. For more than a decade, he masterminded Iran's malevolent and destabilizing work throughout the entire Middle East," McConnell said on the Senate floor as he urged senators to withhold judgment on the operation until they had received the facts.

Supporters of Friday's strike said it restored U.S. deterrence power against Iran, and Trump allies were quick to praise the action. "To the Iranian government: if you want more, you will get more," South Carolina Senator Lindsey Graham tweeted.

"Hope this is the first step to regime change in Tehran," Trump's former national security adviser, John Bolton, wrote in a tweet.

Others, including Democratic White House hopefuls, criticized Trump's order. Democratic presidential candidate Joe Biden said Trump had "tossed a stick of dynamite into a tinderbox," saying it could leave the U.S. "on the brink of a major conflict across the Middle East."

The U.S. urged its citizens to leave Iraq "immediately." The State Department said the embassy in Baghdad, which was attacked by Iran-backed militia and other protesters earlier this week, is closed and all consular services have been suspended.

Iran's next steps

For Iran, the killing represents the loss of a cultural icon who represented national pride and resilience while facing U.S. sanctions. While careful to avoid involving himself in politics, Soleimani's profile rose sharply as the U.S. and Israel blamed him for Iranian proxy attacks abroad.

Iranian President Hassan Rouhani called the killing a "heinous crime" and vowed his country would "take revenge."

Thousands of worshippers in the Iranian capital Tehran took to the streets after Friday Muslim prayers to condemn the killing, waving posters of Soleimani and chanting "Death to deceitful America."

Following Soleimani's death, Khamenei appointed Soleimani's deputy, Brig.-Gen. Esmail Ghaani, to replace him as head of the country's Quds Forces, Iranian media reported.

Protesters demonstrate in Tehran on Friday over the U.S. airstrike in Iraq that killed Soleimani. (Vahid Salemi/The Associated Press)

Iran also summoned the Swiss chargé d'affaires, who represents U.S. interests in Tehran, to protest the killing. "The chargé​​​​ d'affaires was informed of Iran's position and in turn delivered the message of the United States," the ministry said in an emailed response to a Reuters query, without elaborating.

The killing, and any forceful retaliation by Iran, could ignite a conflict that engulfs the whole region. Over the last two decades Soleimani had assembled a network of heavily armed allies stretching all the way to southern Lebanon, on Israel's doorstep.

From criticism to calls for de-escalation

The most immediate impact could be in Iraq. Funerals for Iraqis killed in the attack, including Abu Mahdi al-Muhandis, deputy commander of the Iran-backed militias in Iraq known as the Popular Mobilization Forces, were set for Saturday.

Prime Minister Adel Abdul-Mahdi condemned the strike as an "aggression against Iraq." An emergency session of parliament was called for Sunday, which the deputy speaker, Hassan al-Kaabi, said would take "decisions that put an end to the U.S. presence in Iraq."

Ordering out American forces would heavily damage Washington's influence and make the U.S. troop presence in neighbouring Syria more tenuous. But Iraq's leadership is likely to be divided over such a step. President Barham Salih called for "the voice of reason and wisdom to dominate, keeping in mind Iraq's greater interests."

As U.S. 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."

A photo released by the Iraqi Prime Minister Press Office shows a burning vehicle at the Baghdad International Airport following the airstrike in Baghdad. (Iraqi Prime Minister Press Office via The Associated Press)

France's deputy minister for foreign affairs indicated that urgent reconciliation efforts are being launched behind the scenes. "We are waking up in a more dangerous world. Military escalation is always dangerous," Amelie de Montchalin said on RTL radio.

Russia's Foreign Ministry condemned the killing of Soleimani and said it will increase tensions throughout the Middle East. An unnamed diplomat in the ministry told Russia's state-run news agency TASS they consider the killing "an adventurist step."

China, a close Iranian ally, said it is "highly concerned" and called for all sides, especially the U.S., to exercise "calm and restraint." China is also a staunch opponent of the U.S. presence in Iraq.

U.K. Foreign Minister Dominic Raab urged all parties to de-escalate after the airstrike. "We have always recognized the aggressive threat posed by the Iranian Quds force led by ... Soleimani. Following his death, we urge all parties to de-escalate. Further conflict is in none of our interests," he said in an emailed statement to Reuters.

Pompeo said Friday Washington is committed to "de-escalation."

Canadians urged to leave Iraq

François-Philippe Champagne, Canada's minister of foreign affairs, called on all sides "to exercise restraint and pursue de-escalation."

"Our goal is and remains a united and stable Iraq," he said in a statement.

"Canada has long been concerned by the Islamic Revolutionary Guard Corps' Quds Force, led by ... Soleimani, whose aggressive actions have had a destabilizing effect in the region and beyond," Champagne said, adding that Canada is in contact with its international partners.

Canada's Defence Minister Harjit Sajjan said Friday afternoon he has spoken with his U.S. counterpart.

"Along with our international partners, we are monitoring the situation in Iraq," Sajjan said in a statement. Canada's focus is on the safety of Canadians in the region and helping to build a stable Iraq, he said.

"Canada continues to urge restraint and de-escalation."

Global Affairs Canada said Friday that the risk level for Canadians travelling to Iraq "remains at the highest level."

In a statement to CBC News, a spokesperson for the department said Canadians are advised to "avoid all travel to Iraq," and are "strongly advised" to leave the country if it is safe to do so.

Israel's Netanyahu commends Trump's decision

Israeli Prime Minister Benjamin Netanyahu said Friday the United States had the right to defend itself by killing Soleimani.

"Just as Israel has the right of self-defence, the United States has exactly the same right," Netanyahu said in a statement issued by his office.

"Soleimani is responsible for the death of American citizens and many other innocent people. He was planning more such attacks."

An Israeli soldier stands atop a tank in the Israeli-occupied Golan Heights on Friday. Israel Army Radio said the military had gone on heightened alert following Soleimani's killing. (Hamad Almakt/Reuters)

Netanyahu spoke on the airport tarmac in Greece after cutting short a trip abroad to fly back to Israel.

"President Trump deserves all the credit for acting swiftly, forcefully and decisively. Israel stands with the United States in its just struggle for peace, security and self-defence."

Yoel Guzansky, an expert on Iran at the Institute for National Strategic Studies, a prestigious Tel Aviv think tank, said the killing restored U.S. deterrence powers in the Middle East.

"I think the Iranians are shocked now, the Russians, the Chinese, no one would believe Trump would do that," he said, adding that Iran, in the short run, was likely to retaliate against the U.S. or its allies, and possibly against Israel. But he said in the long run, the loss of Soleimani — who had also been on Israel's radar for some time — would weaken Iran's capabilities across the region.