Tensions between the United States and Iran escalated on Friday after a US air raid killed Qassem Soleimani, head of Iran's elite Quds Force, and Abu Mahdi al-Muhandis, deputy commander of Iran-backed militias known as the Popular Mobilisation Forces, or PMF.

The Pentagon confirmed the attack at Baghdad's international airport, saying it came "at the direction of the president".

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Soleimani and al-Muhandis's deaths are a potential turning point in the Middle East and are expected to draw severe retaliation from Iran and the forces it backs in the region against Israel and US interests.

Here are all the latest updates amid the heightened tensions.

Saturday, January 4:

US senator urges oversight as Iran tension escalates

US Senator Brian Schatz has urged scepticism and "toughest oversight" as the Trump administration ramps up military operations in the Middle East, including the deployment of more troops to Iraq following the death of Iranian military commander Qassem Soleimani.

"They have lied about almost everything. There is no reason to suddenly give them the benefit of the doubt because they took a precipitous military action. Instead, our deepest skepticism, our toughest oversight, our most probing questions, must come now," Schatz wrote on social media.

Opposition members of the US Congress have said President Donald Trump ordered the assassination of Soleimani without congressional authorisation.

Friday, January 3:

White House: Iran retaliation for Soleimani killing would be poor decision

White House national security adviser, Robert O'Brien, said on Friday that any Iranian retaliation in response to the US killing of Soleimani would be a "very poor decision".

O'Brien, briefing reporters on the US operation in a conference call, said Soleimani was struck while travelling around the Middle East planning attacks against American military personnel and diplomats in the region.

Trump: Ordered killing of Iranian general to prevent war, not to start one

US President Donald Trump said he ordered the killing of Qassem Soleimani to stop a war, not to start one, saying the Iranian military commander was planning imminent attacks on Americans.

"Soleimani was plotting imminent and sinister attacks on American diplomats and military personnel but we caught him in the act and terminated him," Trump told reporters at his Mar-a-Lago resort.

"We took action last night to stop a war. We did not take action to start a war," Trump said, adding that the US is not seeking government change in Iran.

3,000 additional US troops heading to Middle East: Officials

The US said it is sending nearly 3,000 more troops to the Middle East with defence officials saying the soldiers are from the 82nd Airborne Division at Fort Bragg, North Carolina.

Speaking on condition of anonymity, the officials said the troops are in addition to approximately 700 soldiers from the 82nd Airborne deployed to Kuwait earlier this week after the storming of the US embassy compound in Baghdad by Iran-backed militiamen and their supporters.

Read more here.

UN chief: 'World cannot afford' another Gulf war

United Nations Secretary-General Antonio Guterres said the "world cannot afford" another Gulf war.

"The secretary-general has consistently advocated for de-escalation in the Gulf," a spokesman for Guterres said in a statement.

"This is a moment in which leaders must exercise maximum restraint. The world cannot afford another war in the Gulf."

Trump: Soleimani behind 'thousands' of US deaths, 'hated' by Iranians

President Trump took to Twitter to defend his decision to kill Soleimani, claiming the Quds Force commander was behind the deaths of "millions of people", including US citizens and his Iranian compatriots.

Soleimani "killed or badly wounded thousands of Americans over an extended period of time, and was plotting to kill many more", Trump said.

"He was directly and indirectly responsible for the death of millions of people, including the recent large number of PROTESTERS killed in Iran itself," he added.

Read more here.

....of PROTESTERS killed in Iran itself. While Iran will never be able to properly admit it, Soleimani was both hated and feared within the country. They are not nearly as saddened as the leaders will let the outside world believe. He should have been taken out many years ago! — Donald J. Trump (@realDonaldTrump) January 3, 2020

Iraqi parliament speaker condemns US attack

The speaker of the Iraqi parliament, Mohammed al-Halbousi, said in a statement: "Yesterday's targeting of a military commander in Iraq's armed forces near Baghdad International Airport is a flagrant breach of sovereignty and violation of international agreements."

"Iraq must avoid becoming a battlefield or a side in any regional or international conflict," he said.

Al-Halbousi called on the government to take all steps needed to stop such attacks.

Dozens of US oil workers leaving Iraq

Dozens of US citizens working for foreign oil companies in the southern Iraqi oil city of Basra were leaving the country on Friday, the oil ministry said.

The US embassy in Baghdad had urged all its citizens to leave Iraq immediately.

Iraqi officials said the evacuation would not affect operations, production or exports.

'US remains committed to de-escalation': Pompeo

Washington is committed to "de-escalation" after a US air raid in Baghdad killed Soleimani, Secretary of State Mike Pompeo said.

Pompeo said on Twitter that he spoke to British Foreign Secretary Dominic Raab and China's top diplomat Yang Jiechi about the US decision to eliminate Soleimani.

Spoke with @HeikoMaas about @realDonaldTrump's decision to take defensive action to eliminate Qassem Soleimani. Germany is also concerned over the Iranian regime's continued military provocations. The U.S. remains committed to de-escalation. — Secretary Pompeo (@SecPompeo) January 3, 2020

Soleimani's body to be sent to Iran

Flags at Iranian embassies abroad were ordered to fly at half-staff and preparations were being made for Soleimani's body to be repatriated to Iran. The date for the funeral is yet to be announced.

Responding to the US assassination of Soleimani, Iran's National Security Council spokesman Keyvan Khosravi said: "The legal, political, security, and military consequences of this crime is on the US government."

"The costs that Washington has to pay will be much more severe than the mirage-like achievements of this sort of blind moves," he added.

Tens of thousands rally against 'US crimes'

Tens of thousands of people took to the streets in Iran to protest against US "crimes", after US raids killed Soleimani.

Chanting "Death to America" and holding up posters of the slain commander, demonstrators filled streets for several blocks in central Tehran after Friday prayers.

State news agency IRNA reported similar demonstrations in the cities of Arak, Bojnourd, Hamedan, Hormozgan, Sanandaj, Semnan, Shiraz and Yazd.

Protesters in Tehran demonstrated against the killing of Qassem Soleimani [Vahid Salemi/The Associated Press]

Khamenei appoints Soleimani's successor

Iran's supreme leader appointed Esmail Qaani as the new head of the IRGC's foreign operations arm.

"Following the martyrdom of the glorious General Haj Qassem Soleimani, I name Brigadier General Esmail Qaani as the commander of the Quds Force of the Islamic Revolutionary Guard Corps," Ayatollah Ali Khamenei said in a statement posted on his official website.

In Pictures: Iran's Qassem Soleimani killed in US air raid

This photo released by the Iraqi prime minister's press office shows a burning vehicle at Baghdad International Airport following the air attack [The Associated Press]

Click here for further images related to the Soleimani killing.

US urges citizens to leave Iraq 'immediately'

The US is urging all its citizens to leave Iraq "immediately", citing "heightened tensions in Iraq and the region".

A State Department statement added: "Due to Iranian-backed militia attacks at the US Embassy compound, all consular operations are suspended. US citizens should not approach the Embassy."

This comes after a crowd attempted to storm the embassy in Baghdad earlier this week to protest against US air raids aimed at the Popular Mobilisation Forces.

Hezbollah to continue on Soleimani's path after US attack: Report

Lebanon's Hezbollah leader Sayyed Hassan Nasrallah said his group would continue the path of Soleimani after his death, broadcaster Al Manar reported.

Nasrallah said the US would not be able to achieve its goals with this "big crime" and just punishment was the responsibility of all fighters, Al Manar reported.

Israel's military on high alert

Israel's military had gone on heightened alert amid fears that Iran could strike through its regional allies such as Hezbollah to the north or through Palestinian groups Hamas and Islamic Jihad in Gaza.

Israel's foreign ministry and defence officials announced a high-security alert at Israel's overseas delegations, fearing retaliation.

Israel's defence minister summoned the country's military and security chiefs to Tel Aviv in the wake of the assassination. Meanwhile, Prime Minister Benjamin Netanyahu has reportedly cut short his trip to Greece.

Syria condemns killing of Soleimani: State news agency

Syria strongly condemns the "treacherous, criminal American aggression" that led to the killing of Iranian Major-General Soleimani, state news agency SANA cited a foreign ministry source as saying.

The source said the attack constituted a "serious escalation" and reaffirmed US responsibility for instability in Iraq, according to SANA.

Iraq's Sadr mourns Soleimani, reactivates Mahdi army

Iraq's prominent Shia leader Muqtada al-Sadr said the killing of Soleimani targeted Iraq's opposition and "Jihad", adding that it will not weaken its resolve.

In a statement, al-Sadr called on his militias (Army of Imam Mahdi) and "other national and disciplined" armed groups to be prepared to protect Iraq. He also expressed his condolences to Iran.

Qais al-Khazali, the head of the Asaib Ahl al-Haq armed faction, said: "All fighters should be on high alert for upcoming battle and great victory."

"The end of Israel and removal of the US from the region will be the result of the assassination of Soleimani and Muhandis," he said in a statement published by Iraqi media.

Pro-Hezbollah newspaper Al Akhbar: 'It is war'

Lebanese pro-Hezbollah newspaper Al Akhbar is leading with a comment by its contributor Hassan Alaiq on the killing of Soleimani.

The Arabic article has a simple headline: The martyrdom of Soleimani: It is war

Who was Soleimani, Iran's IRGC leader?

Soleimani acquired celebrity status at home and abroad as the leader of the Quds Force, the foreign arm of Iran's elite Islamic Revolutionary Guard Corps (IRGC) and for his key role in fighting in Syria and Iraq.

He survived several assassination attempts against him by Western, Israeli and Arab agencies over the past 20 years. Read more here.

Al Jazeera's Charlotte Bellis reports on the life of Iran's most important general.

Former top Iranian commander: 'We will take vigorous revenge'

"He joined his martyred brothers, but we will take vigorous revenge on America," Mohsen Rezaei, a former commander of the IRGC who is now the secretary of a powerful state body, said in a post on Twitter.

Khamenei warns of harsh revenge

Iran's Supreme Leader Ayatollah Khamenei called for three days of mourning, saying Major General Soleimani's killing will double the motivation of the resistance against the US and Israel.

According to Iranian state television, Khamenei said harsh revenge awaits the "criminals" who killed Soleimani.

Top House Democrats: Strikes not authorised by Congress

US Democratic congressional leaders issued statements condemning President Donald Trump ordering the attacks that killed Soleimani, saying the president did not obtain congressional approval.

"American leaders' highest priority is to protect American lives and interests. But we cannot put the lives of American servicemembers, diplomats and others further at risk by engaging in provocative and disproportionate actions," said House Speaker Nancy Pelosi.

"The Administration has conducted tonight's strikes in Iraq targeting high-level Iranian military officials and killing Iranian Quds Force Commander Qasem Soleimani without an Authorization for Use of Military Force (AUMF) against Iran. Further, this action was taken without the consultation of the Congress," she added, calling for a briefing on the situation.

Another top Democrat, Adam Schiff, took to Twitter, saying the "American people don't want a war with Iran".

Soleimani was responsible for unthinkable violence and world is better off without him.



But Congress didn't authorize and American people don't want a war with Iran.



All steps must now be taken to protect our forces against the almost inevitable escalation and increased risk. https://t.co/Z4HTnScFg7 — Adam Schiff (@RepAdamSchiff) January 3, 2020

Oil prices surge after Soleimani's killing

Oil prices jumped more than 4 percent on Friday after news of Soleimani's death.

Brent crude futures were up by nearly $3 at $69.16 per barrel, their highest since September 17, as markets feared Iran could retaliate against the killing of its top militiamen by attacking assets belonging to the US and their allies in the Middle East.

Read more here.

Biden: Trump just tossed dynamite in a tinderbox

Former vice president and Democratic presidential frontrunner Joe Biden said while Soleimani deserved to be brought to justice, Trump "just tossed a stick of dynamite into a tinderbox".

Biden posted the statement on Twitter.

"The Administration's statement says that its goal is to deter future attacks by Iran, but this action will almost certainly have the opposite effect," he said. "President Trump just tossed a stick of dynamite into a tinderbox, and he owes the American people an explanation of the strategy and plan to keep safe our troops and embassy personnel, our people and our interests, both here at home and abroad, and our partners throughout the region and beyond."

My statement on the killing of Qassem Soleimani. pic.twitter.com/4Q9tlLAYFB — Joe Biden (@JoeBiden) January 3, 2020

Pompeo tweets video he says is of Iraqis dancing in the streets

"Iraqis - Iraqis - dancing in the street for freedom; thankful that General Soleimani is no more," Pompeo tweeted along with a video.

Iraqis — Iraqis — dancing in the street for freedom; thankful that General Soleimani is no more. pic.twitter.com/huFcae3ap4 — Secretary Pompeo (@SecPompeo) January 3, 2020

More members of US Congress react to US strikes in Iraq

Several members of Congress took to Twitter to react to Trump-ordered raids that killed Soleimani. Republicans praised the move, while many Democrats questioned the US president's ability to order such an attack.

Senator and Democratic presidential hopeful Elizabeth Warren said: "Soleimani was a murderer, responsible for the deaths of thousands, including hundreds of Americans. But this reckless move escalates the situation with Iran and increases the likelihood of more deaths and new Middle East conflict. Our priority must be to avoid another costly war."

Soleimani was a murderer, responsible for the deaths of thousands, including hundreds of Americans. But this reckless move escalates the situation with Iran and increases the likelihood of more deaths and new Middle East conflict. Our priority must be to avoid another costly war. — Elizabeth Warren (@ewarren) January 3, 2020

Republican House Minority Leader Kevin McCarthy said: "Soleimani was a terrorist. President Trump and our brave servicemembers just reminded Iran - and the world - that we will not let attacks against Americans go unpunished."

Soleimani was a terrorist. President Trump and our brave servicemembers just reminded Iran—and the world—that we will not let attacks against Americans go unpunished.



🇺🇸 — Kevin McCarthy (@GOPLeader) January 3, 2020

Independent Representative Justin Amash said: "There's a reason our Constitution grants Congress the power to declare war: Every American may be intimately affected by a violent conflict. Soleimani was evil. But our system demands consent for war from the people, acting through their representatives and senators in Congress."

There's a reason our Constitution grants Congress the power to declare war: Every American may be intimately affected by a violent conflict. Soleimani was evil. But our system demands consent for war from the people, acting through their representatives and senators in Congress. — Justin Amash (@justinamash) January 3, 2020

Republican Senator Lindsey Graham tweeted: "Thank you, Mr. President, for standing up for America."

Thank you, Mr. President, for standing up for America. — Lindsey Graham (@LindseyGrahamSC) January 3, 2020

Democratic Senator Ed Markey said on Twitter: "Trump's apparent assassination of Soleimani is a massive, deliberate, and dangerous escalation of conflict with Iran. The President just put the lives of every person in the region - U.S. service members and civilians - at immediate risk. We need de-escalation now."

Trump's apparent assassination of Soleimani is a massive, deliberate, and dangerous escalation of conflict with Iran. The President just put the lives of every person in the region - U.S. service members and civilians - at immediate risk.



We need de-escalation now. https://t.co/oAenBUsvFl — Ed Markey (@SenMarkey) January 3, 2020

Iran's Zarif: US 'act of terrorism ... is foolish escalation'

Iran's Minister of Foreign Affairs Mohammad Javad Zarif warned on Twitter that the US "bears responsibility or all consequences" of its attack killing Soleimani.

"The US' act of international terrorism, targeting & assassinating General Soleimani - THE most effective force fighting Daesh (ISIS), Al Nusrah, Al Qaeda et al - is extremely dangerous & a foolish escalation," Zarif tweeted. "The US bears responsibility for all consequences of its rogue adventurism."

The US' act of international terrorism, targeting & assassinating General Soleimani—THE most effective force fighting Daesh (ISIS), Al Nusrah, Al Qaeda et al—is extremely dangerous & a foolish escalation.



The US bears responsibility for all consequences of its rogue adventurism. — Javad Zarif (@JZarif) January 3, 2020

PMF spokesman: 'US and Israeli enemy responsible'

Ahmed al-Assadi, a spokesman for the PMF, blamed the US and Israel for Friday's strikes.

"The American and Israeli enemy is responsible for killing the mujahideen Abu Mahdi al-Muhandis and Qassem Soleimani," he was quoted by Reuters News Agency as saying.

Iran state broadcaster confirms Soleimani was 'martyred'

Citing an IRGC statement, Iranian state television said Soleimani was "martyred" in an attack by US helicopters near the airport, without elaborating.

Pentagon confirms Soleimani killed at 'direction of the president'

The Pentagon confirmed in a statement that Soleimani was killed "at the direction" of President Trump.

"At the direction of the President, the US military has taken decisive defensive action to protect US personnel abroad by killing Qasem Soleimani," a Pentagon statement said.

"This strike was aimed at deterring future Iranian attack plans. The United States will continue to take all necessary action to protect our people and our interests wherever they are around the world."

At the direction of the President, the U.S. military has taken decisive defensive action to protect U.S. personnel abroad by killing Qasem Soleimani, the head of the Iranian Revolutionary Guard Corps-Quds Force, a US-designated Foreign Terrorist Organization. — The White House (@WhiteHouse) January 3, 2020

Trump tweets image of American flag

President Trump did not comment on the US raids but, shortly after reports surfaced, he tweeted a picture of an American flag.

Senator Murphy: Did Trump set off a potential regional war?

US Democratic Senator Chris Murphy questioned whether Trump needed congressional approval to target Soleimani.

"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?"

Soleimani was an enemy of the United States. That's not a question.



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? — Chris Murphy (@ChrisMurphyCT) January 3, 2020

Senator Rubio: Quds Force chose the path of escalation

US Republican Senator Marco Rubio tweeted that Iran's "Quds Force chose the path of escalation".

"Facing repeated #IRGC attacks the U.S. & @potus exercised admirable restraint while setting clear red lines & the consequences for crossing them

"#Iran's Quds Force chose the path of escalation They are entirely to blame for bringing about the dangerous moment now before us."

The defensive actions the U.S. has taken against #Iran & its proxies are consistent with clear warnings they have received



They chose to ignore these warnings because they believed @POTUS was constrained from acting by our domestic political divisions



They badly miscalculated — Marco Rubio (@marcorubio) January 3, 2020

Former Pentagon official: 'No doubt' US wanted to target Soleimani

Speaking to Al Jazeera, US Assistant Secretary of Defense Lawrence Korb said "there is no doubt" that the US had wanted to target Soleimani "for a while".

Soleimani killed in US raid at Baghdad airport

Major General Qassem Soleimani, head of Iran's elite Quds Force, was reported killed along with six others following an air raid at Baghdad's international airport.

Iraqi officials and the state television reported that, aside from Soleimani, Iraqi militia commander Abu Mahdi al-Muhandis was also killed in the attack.

Read more here.

Read more about recent events that led to the heightened tensions

Iraq: Anti-government protesters denounce pro-Iran crowds

Iran may be planning attacks on US interests: Pentagon chief

Pro-Iran protesters leave US embassy compound in Baghdad

'Iran is not afraid': Why Tehran dismisses US threats over Iraq

US caught off guard as protesters storm Baghdad embassy: Analysts