US President Donald Trump has warned he has a list of "52 Iranian targets" he would "hit very fast and very hard", while Iranian MPs have chanted "death to America".
As tensions continue to rise and thousands mourn Major General Qassem Soleimani for a second day, Mr Trump's tweets have been blasted by Iran as a threat of war crimes.
Speaking about video showing the politicians' chanting, Sky News' foreign editor Deborah Haynes said: "These are MPs. It's like having the entire UK parliament standing up and chanting. It's absolutely extraordinary."
It comes after a string of tweets by the US president about the protection of US assets following the killing of Major General Qassem Soleimani.
He wrote: "Iran is talking very boldly about targeting certain USA assets as revenge for our ridding the world of their terrorist leader who had just killed an American, & badly wounded many others, not to mention all of the people he had killed over his lifetime, including recently hundreds of Iranian protesters," the US president wrote on Twitter.
"He was already attacking our embassy , and preparing for additional hits in other locations. Iran has been nothing but problems for many years.
"Let this serve as a WARNING that if Iran strikes any Americans, or American assets, we have targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD.
"The USA wants no more threats!"
Mr Trump went on to say that the US has recently spent "two trillion dollars on military equipment".
"We are the biggest and by far the BEST in the World! If Iran attacks an American Base, or any American, we will be sending some of that brand new beautiful equipment their way...and without hesitation!" he tweeted.
Iran's foreign minister Javad Zarif responded to Mr Trump's threats, saying they were a breach of international law.
He tweeted: "Having committed grave breaches of international law in Friday's cowardly assassinations, @realdonaldtrump threatens to commit again new breaches of jus cogens; targeting cultural sites is a war crime; whether kicking or screaming, end of US malign presence in West Asia has begun.
"Those masquerading as diplomats and those who shamelessly set to identify Iranian cultural & civilian targets should not even bother to open a law dictionary.
"Jus cogens refers to peremptory norms of international law, ie international red lines. That is, a big(ly) 'no no'."
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His comments came shortly after a rocket fell near the US embassy in Baghdad .
There were no casualties after the rocket fell near the embassy compound in the Iraqi capital's green zone, police sources told Reuters.
Two Katyusha rockets have also fallen near Iraq's Balad air base, which houses US forces. No casualties have been reported following this incident.
Separately, mortar has fallen in Baghdad's Jadriya neighbourhood - with police sources telling Reuters that five people have been wounded.
Iran has said it will punish Americans within reach of the country after Maj Gen Soleimani , head of the country's elite Quds force and mastermind of its regional security strategy, was killed in a US airstrike on his motorcade early on Friday near the Iraqi capital's international airport.
A funeral procession took place on Saturday for Maj Gen Soleimani and Iraqi militant leaders, including paramilitary chief Abu Mahdi al Muhandi, and eight others who died.
Mourners - mostly men in black military fatigues - carried Iraqi flags and the flags of Iran-backed militias who are fiercely loyal to Maj Gen Soleimani.
Iraq's foreign minister Javad Zarif tweeted on Saturday: "24hrs ago, an arrogant clown - masquerading as a diplomat - claimed people were dancing in the cities of Iraq.
"Today, hundreds of thousands of our proud Iraqi brothers and sisters offered him their response across their soil."
Chants of "No, no, America" and "Death to America, death to Israel" were heard, as well as "America is the Great Satan".
Two helicopters hovered over the procession, which was attended by Prime Minister Adel Abdul-Mahdi and leaders of Iran-backed militias.
Maj Gen Soleimani's body has now been taken back to Iran.
Following the funeral, Tasnim news agency quoted a senior Revolutionary Guard commander saying Iran will punish Americans wherever they are within reach of the country.
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General Gholamali Abuhamzeh said Iran had identified 35 US targets in the region, including in Tel Aviv and ships in the Gulf.
"The Strait of Hormuz is a vital point for the West and a large number of American destroyers and warships cross there," he said.
In the hours after the airstrike, Iranian defence minister Amir Hatami threatened "crushing revenge" and Iran's supreme leader, Ayatollah Ali Khamenei, said there would be "harsh retaliation".
Iranian President Hassan Rouhani added: "Soleimani's martyrdom will make Iran more decisive to resist America's expansionism and to defend our Islamic values."
On Friday, Mr Trump said the US carried out the airstrike because Maj Gen Soleimani had been planning "imminent and sinister attacks on US diplomats and military personnel".
An official with the US-led coalition in Iraq said operations have been scaled back and "security and defensive measures" have been boosted at bases hosting coalition forces.
An extra 3,000 US troops have been dispatched to neighbouring Kuwait.
A growing number of US Democrats have accused President Trump of bringing the US to the brink of war.
House Speaker Nancy Pelosi said "the Trump Administration's provocative, escalatory and disproportionate military engagement continues to put servicemembers, diplomats and citizens of America and our allies in danger".
Iraq - a close US and Iran ally - condemned the airstrike and called it an attack on its national sovereignty.
Its parliament will meet for an emergency session later on Sunday as it comes under pressure to expel the 5,200 American troops based in the country to help prevent an Islamic State resurgence.