Iran is considering 13 'revenge scenarios' in retaliation for the US airstrike that killed General Qassem Soleimani in Iraq, a top official has said.

Ali Shamkhani, secretary of Iran's Supreme National Security Council, vowed that even if Tehran opted for the weakest option, it will create an 'historic nightmare for the Americans'.

While Shamkhani would not reveal any specific details of the plans, he said all US forces in the Middle East are being considered for strikes.

Ali Shamkhani, secretary of Iran's Supreme National Security Council (centre), revealed Tehran is considering 13 'revenge scenarios' in retaliation for the killing of General Soleimani

Even if the security council votes for the weakest option it will mean an 'historic nightmare for the Americans', Shamkani warned (pictured, a protester in Iran)

He said that US bases across Iraq are being kept under close surveillance and claimed to know the exact number of personnel and equipment being kept at each.

'We insist that all troops be withdrawn,' he said, according to Iranian newspaper Resalat. 'If the troops want to dig into the bases, we will destroy the bases in addition to the troops.

'Those who crawl into shelters and close the doors hoping to escape our revenge are unaware that the Islamic Republic will open the door to hell.'

He later added: 'If the US troops do not leave our region voluntarily and upright, we will do something to carry their bodies out horizontally.'

Iran has vowed to exact a 'crushing revenge' over the killing of Soleimani, which is expected to ramp up Tuesday after a three-day period of mourning ends.

The country has already ripped up what remained of the nuclear deal signed under Obama in the wake of the strike, and Iraq has voted to kick all US troops out.

Rockets have also been launched at the Green Zone surrounding the US embassy in Baghdad, with the area expected to come under increasing attacks.

While Iran has not made its future plans clear, some 5,000 US troops stationed across Iraq and 500 still in Syria are expected to be targeted in response.

Hassan Nasrallah, the Lebanese secretary-general of Iran-backed Hezbollah, said all US bases, all warships and every single soldier in the region is now a target.

'The true, just retribution for those who conducted this assassination is an institution, which is the U.S. military,' he said during a ceremony to mourn Soleimani's death in Beirut on Sunday.

'We will launch a battle against those killers, those criminals.'

US intelligence believes that Iran will try to kill one of its top generals in the region in a tit-for-tat slaying.

One official said the U.S. anticipates a 'major' attack of some type within the next day or two.

Iranian lawmakers holding pictures of slain Iran's Quds Force leader Qasem Soleimani as they chant 'death to America' during a session on Tuesday

Iran's response to Soleimani's killing is expected to ramp up Tuesday when a three-day period of mourning comes to an end (pictured, funeral procession in his home town of Kerman)

The U.S. military has increased protection of its forces, particularly in Iraq.

Six long-range B-52 bombers have also been stationed on Diego Garcia, a British-controlled island in the Indian ocean - putting them out of range of Iranian missiles but within striking distance of the country.

Pentagon officials said the B-52s will be available for operations against the Islamic Republic if ordered into action.

Meanwhile the US Air Force put on a show of strength in Utah, after carrying out a training exercise with 52 F-35A Lightining II stealth fighters.

'We're ready to fly, fight, and win,' the 419th Fighter Wings tweeted after the exercise.

They added the exercise 'pushed the boundaries and tested our Airmen's ability to deploy the F-35As en masse'

The 52 F-35A aircrafts, which are worth a whopping $4.2 billion, took off in quick succession from the Hill Air Force Base in Utah on Monday following an elephant walk down the runway

NATO has said it is withdrawing 'some personnel' from Iraq over fears for their safety, after cancelling a training exercise on Saturday.

Iran's parliament passed a bill on Tuesday designating all US forces 'terrorists' over the killing.

Under the newly adopted bill, all US forces and employees of the Pentagon and affiliated organisations, agents and commanders and those who ordered the 'martyrdom' of Soleimani were designated as terrorists.

'Any aid to these forces, including military, intelligence, financial, technical, service or logistical, will be considered as co-operation in a terrorist act,' the Iranian parliament said.

According to reports on social media, Iranian lawmakers chanted 'Death to America' while voting for passage of the bill.

Lawmakers also voted to bolster by £170million the coffers of the Quds Force - the foreign operations arm of Iran's Revolutionary Guards that was headed by Soleimani.

The bill was an amended version of a law adopted in April last year that declared the United States a 'state sponsor of terrorism' and its forces in the region 'terror groups'.

A U.S. Air Force pilot takes off in his Air Force F-35A aircraft from the 388th and 428th Fighter Wings to participate in the combat power exercise

Iran's top security body, the Supreme National Security Council, said that blackisting came after the US designated Iran's Revolutionary Guards a 'terrorist organisation'.

Iran and America have careened from one flare-up to another since Trump began his 'maximum pressure' campaign against Iran shortly after taking office.

He tore up the 2015 nuclear deal and reimposed crushing economic sanctions, both steps aimed at preventing Iran from getting a nuclear weapon and deterring the sort of regional aggression spearheaded by Soleimani.

Two U.S. officials, speaking on condition of anonymity to discuss internal discussions, said targeting Soleimani was not representative of a wholesale shift in American policy toward Iran, despite Secretary of State Mike Pompeo's comments on Sunday that the U.S. was targeting Iran's 'actual decision-makers' rather than its network of proxy allies.

Trump has repeatedly contended that he is not seeking 'regime change' in Iran, as has been pushed by some of his more hawkish advisers.

Still, Trump's strike against Soleimani, a revered figure in Iran whose death sparked large displays of anger and grief, was a risky decision his Republican and Democratic predecessors opted not to take out of concern it would draw the U.S. and Iran closer to conflict.

The Pentagon is deploying six B-52 Stratofortress bombers (like the ones seen in the above stock image) to a military base in the northern Indian Ocean, according to a CNN report from Monday

The strategic bombers were on their way Monday to Diego Garcia, an atoll that is home to a vital US military base

U.S. officials are also aware that Iran could try to strike a high-level American leader in a 'tit-for-tat' move, potentially a military commander.

One official said some Iranian ships have spread out, and while the intent isn´t immediately clear, they could move rapidly to attack.

The U.S. military has increased protection of its forces, particularly in Iraq. Officials said a number of the recently deployed soldiers from the 1st Brigade of the 82nd Airborne Division had moved into Iraq from Kuwait in order to increase security for Americans there.

The U.S. military has stopped all training of Iraqi forces to focus on force protection, officials said.

As of Monday, officials said, there had not been a broadly distributed order or recommendation to increase security at military installations worldwide. Instead, decisions were being left up to the commanders.