TEHERAN (AP) - Weeping amid wails from a crowd of hundreds of thousands of mourners, Iran's supreme leader on Monday (Jan 6) prayed over the remains of a top Iranian general killed in a United States air strike in Baghdad, an attack that has drastically raised tensions between Teheran and Washington.

The targeted killing of Iranian Revolutionary Guard Major-General Qassem Soleimani already has seen his replacement vow to take revenge.

Additionally, Teheran has abandoned the remaining limits of its 2015 nuclear deal with world powers in response to the slaying, while in Iraq, the Parliament has called for the expulsion of all American troops from Iraqi soil.

The developments could bring Iran closer to building an atomic bomb, set off a proxy or military attack launched by Teheran against America and enable the Islamic State in Iraq and Syria (ISIS) group to stage a comeback in Iraq, making the Middle East a far more dangerous and unstable place.

Adding to the tensions, President Donald Trump threatened to demand billions of dollars in compensation from Iraq or impose "sanctions like they've never seen before" if it goes through with expelling US troops.

Maj-Gen Soleimani's daughter, Zeinab, directly threatened an attack on the US military in the Middle East while speaking to a crowd of hundreds of thousands in Teheran that stretched as far as the eye could see.

Iranian state TV put the crowd size at "millions", though that number could not be verified.

"The families of the American soldiers in western Asia... will spend their days waiting for the death of their children," she said to cheers.

Iran's Supreme Leader Ayatollah Ali Khamenei himself prayed over the caskets of Maj-Gen Soleimani and others slain in the attack. Ayatollah Khamenei, who had a close relationship with Maj-Gen Soleimani, wept at one point during the traditional Muslim prayers for the dead. The crowd wailed.

Maj-Gen Soleimani's successor, Maj-Gen Esmail Ghaani, stood near Ayatollah Khamenei's side, as did Iranian President Hassan Rouhani and other top leaders in the Islamic Republic.

While Iran recently faced nationwide protests over government-set gasoline prices that reportedly killed over 300 people, Maj-Gen Soleimani's mass processionals have seen politicians and leaders across the Islamic Republic's political spectrum take part, temporarily silencing that anger.

Maj-Gen Ghaani made his own threat in an interview with Iranian state television aired on Monday.

"God the almighty has promised to get his revenge, and God is the main avenger. Certainly actions will be taken," he said.

Maj-Gen Ghaani, a long-time Soleimani deputy, has now taken over as the head of the Revolutionary Guard's Quds Force, an expeditionary arm of the paramilitary organisation answerable only to Ayatollah Khamenei.

Maj-Gen Ghaani has been sanctioned by the US since 2012 for his work funding its operations around the world, including its work with proxies in Iraq, Lebanon and Yemen.

Those proxies likely will be involved in any operation targeting US interests in the Middle East or elsewhere in the world.

Already, the US Embassy in Saudi Arabia warned Americans "of the heightened risk of missile and drone attacks".

In Lebanon, the leader of the Iranian-backed militant group Hezbollah said Maj-Gen Soleimani's killing made US military bases, warships and service members across the region fair game for attacks.

A former Iranian Revolutionary Guard leader suggested the Israeli city of Haifa and others could be targeted should the US attack Iran.

"We promise to continue down martyr Soleimani's path as firmly as before with help of God, and in return for his martyrdom we aim to get rid of America from the region," Maj-Gen Ghaani said.

The head of the Guard's aerospace programme, Brigadier General Amir Ali Hajizadeh, suggested Iran's response wouldn't stop with a single attack.

"Firing a couple of missiles, hitting a base or even killing (Donald) Trump is not valuable enough to compensate for martyr Soleimani's blood," Brig-Gen Hajizadeh said on state TV.

"The only thing that can compensate for his blood is the complete removal of America from the region and taking away their evil from the oppressed people of the region."

On the nuclear deal, Iranian state television cited Sunday a statement by Mr Rouhani's administration saying the country would not observe the nuclear deal's restrictions on fuel enrichment, on the size of its enriched uranium stockpile and on its research and development activities.

German Chancellor Angela Merkel, French President Emmanuel Macron and British Prime Minister Boris Johnson specifically urged Iran to "withdraw all measures" not in line with the 2015 agreement that was intended to stop Teheran from pursuing its atomic weapons programme.

Iran insisted that it remains open to negotiations with European partners over its nuclear programme. And it did not back off from earlier promises that it wouldn't seek a nuclear weapon.

However, the announcement represents the clearest nuclear proliferation threat yet made by Iran since Mr Trump unilaterally withdrew from the accord in 2018 and reimposed sanctions last year.

It further raises regional tensions, as Iran's long-time foe Israel has promised never to allow Iran to produce an atomic bomb.

Iran did not elaborate on what levels it would immediately reach in its programme.

Teheran has already broken some of the deal's limits as part of a step-by-step pressure campaign to get sanctions relief.

It already has increased its production, begun enriching uranium to 5 per cent and restarted enrichment at an underground facility.

While it does not possess uranium enriched to weapons-grade levels of 90 per cent, any push forward narrows the estimated one-year "breakout time" needed for it to have enough material to build a nuclear weapon if it chose to do so.

The International Atomic Energy Agency (IAEA), the United Nations watchdog observing Iran's programme, did not respond to a request for comment.

However, Iran said that its cooperation with the IAEA "will continue as before".

Maj-Gen Soleimani's killing has escalated the crisis between Teheran and Washington after months of back-and-forth attacks and threats that have put the wider Middle East on edge.

Iran has promised "harsh revenge" while Mr Trump has vowed on Twitter that the US will strike back at 52 targets "very fast and very hard".

He doubled down on that threat on Sunday, dismissing warnings that targeting cultural sites could be a war crime under international law.

"They're allowed to kill our people. They're allowed to torture and maim our people. They're allowed to use roadside bombs and blow up our people. And we're not allowed to touch their cultural sites? It doesn't work that way," Mr Trump told reporters.

On Sunday, hundreds of thousands of mourners accompanied the coffin carrying Maj-Gen Soleimani's remains in the Iranian cities of Ahvaz and Mashhad.

A similar procession was expected in Qom and Teheran on Monday. Tens of thousands already filled the streets of the Iranian capital on Monday morning.

Mourners wearing black beat their chests and carried posters with Maj-Gen Soleimani's portrait. Demonstrators also unfurled red Shi'ite flags, which traditionally symbolise both the spilled blood of someone unjustly killed and a call for vengeance.

The processions mark the first time Iran honoured a single man with a multi-city ceremony.

Not even Ayatollah Ruhollah Khomeini, who founded the Islamic Republic, received such a processional with his death in 1989.

Maj-Gen Soleimani on Monday will lie in state at Teheran's famed Musalla mosque as the revolutionary leader did before him.

He will be buried in his hometown of Kerman.