Chanting "Death to America", the Hashed al-Shaabi loyalists filled a Baghdad square to honour Iranian General Qasem Soleimani, who headed the Quds Force, the foreign operations arm of Iran's Revolutionary Guards, until his death on January 3, 2020.

The night-time drone strike near Baghdad airport sent shock waves across the region and sparked fears that decades of arch enmity between Washington and regional Shiite power Tehran would escalate into direct military confrontation.

"US terrorism has to end," read one sign at the rally by backers of the pro-Iranian Hashed, a Shiite former paramilitary alliance that has been integrated into Iraq's state security apparatus.

The strike against Soleimani, the architect of Iran's Middle Eastern military strategy, was ordered by then US president Donald Trump, and it also killed his Iraqi lieutenant Abu Mahdi al-Muhandis, the Hashed's deputy chief.

Hashed supporters, some with their children, marched into a square in central Baghdad that was closed off to traffic, an AFP correspondent said.

Some unfurled huge white flags emblazoned with the Hashed insignia, as well as Iraq's national flag, while others held pictures of Soleimani and Muhandis.

- Unclaimed attacks -

The US said at the time that Soleimani was planning imminent action against US personnel in Iraq, a country long torn between the competing demands of its principal allies Washington and Tehran, and the assassination came after a wave of attacks on US interests in the country.

Iran, which wields considerable cross-border influence, warned it would avenge Soleimani's death.

Five days after his killing, it fired missiles at an air base in Iraq housing US troops and another near Arbil in the country's north.

Since then dozens of rockets and roadside bombs have targeted US security, military and diplomatic sites across Iraq.

Iraqi and Western officials have blamed hard-line pro-Iran factions for the attacks, which have never been claimed by any group.

In February last year, the US carried out an air strike against Kataeb Hezbollah, an Iranian-backed Iraqi paramilitary force stationed along the Iraqi-Syrian border, following rocket attacks on its Baghdad embassy and a US military contracting firm north of the capital.

The Hashed has repeatedly called for the withdrawal of US troops deployed in Iraq as part of a multinational coalition fighting Islamic State group jihadists.

The Sunni extremists seized around a third of Iraq in a lightning 2014 offensive, but were beaten back by both the US-led coalition and the Hashed, before Baghdad declared the jihadists defeated in late 2017.

- 'Crime against sovereignty' -

Senior Hashed official Faleh al-Fayyad reiterated the demand that the US complete its withdrawal Saturday, saying the killing of Soleimani and Muhandis was "a crime against Iraqi sovereignty".

In December, Iraq announced the end of the US-led coalition's "combat mission" in the country.

But about 2,500 American soldiers and 1,000 coalition troops are to remain deployed in Iraq to offer training, advice and assistance to national forces.

The Hashed's political wing, the Fatah (Conquest) Alliance, performed very strongly in the 2018 legislative elections, thanks to the paramilitaries' key role in defeating IS.

While Fatah remains a significant political player, it lost almost two thirds of its seats in legislative polls in October, driven by concerns even among Shiite voters over outsized Iranian influence.

As part of the anniversary commemorations, a candle-lit vigil is set to take place on Sunday evening at Baghdad airport.

In Iran, Supreme Leader Ayatollah Ali Khamenei and senior Guards figures met with Soleimani's family on Saturday, ahead of the main commemorations there on Monday.