At least 18 people have been killed and 800 wounded in Iraq when masked security forces opened fire on protesters in the Shia holy city of Karbala on Tuesday, security officials have said.

The overnight attack targeted a protest camp erected in the city’s Education Square just 2km from the famed Imam Hussein Shrine, according to witnesses.

Video footage reportedly taken at the scene and shared online showed demonstrators running for cover, as a constant volley of machine gunfire crackled in the background.

Amnesty International and Karbala’s health department chief issued a lower toll. The rights group said at least 14 had been killed and more than 100 people were injured.

It urged the Iraqi authorities to “immediately rein in” its security forces saying they had used “excessive and lethal force”.

The city’s police chief and governor denied the killings took place in public statements.

Iraq protests: Death toll soars as live rounds and tear gasfire Show all 17 1 /17 Iraq protests: Death toll soars as live rounds and tear gasfire Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi protesters take cover behind a barricade on Al-Jumhuriya Bridge during an anti-government demonstration in the Iraqi capital Baghdad on 25 October, 2019. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Protesters push down concrete walls during a protest over corruption, lack of jobs, and poor services, in Baghdad. Reuters Iraq protests: Death toll soars as live rounds and tear gasfire Anti-government protesters try to break into the provincial council building during a demonstration in Basra. AP Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi women protesters march with national flags during an anti-government demonstration in the central holy shrine city of Najaf. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire An Iraqi protester uses a mobile phone to take a selfie photo with an army soldier standing atop a humvee during a demonstration outside the local government headquarters in the southern city of Basra. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi protesters gather during an anti-government demonstration at the burning local government headquarters in Nasiriyah, the capital of Iraq's southern province of Dhi Qar. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi protesters wave a national flag as they stand atop the gatehouse to the local government headquarters in the southern city of Basra. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire An Iraqi protester throws back a tear gas canister fired by security forces amid clashes during an anti-government demonstration in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi protesters carry away an injured protester following clashes during an anti-government demonstration in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi security forces stand guard on Al-Jumhuriya Bridge during an anti-government demonstration in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Anti-government protesters gather in Tahrir Square during a demonstration in central Baghdad. AP Iraq protests: Death toll soars as live rounds and tear gasfire The burning local government headquarters in Nasiriyah, the capital of Iraq's southern province of Dhi Qar. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Protesters take cover behind a concrete barricade during a demonstration in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi paramedics help injured protesters in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Iraqi protesters gather in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire An Iraqi protester takes cover between concrete barricades in Baghdad. AFP/Getty Iraq protests: Death toll soars as live rounds and tear gasfire Protesters take cover from teargas canisters fired by security forces in Baghdad. AFP/Getty

But security officials, speaking on the condition of anonymity, confirmed that 18 were killed.

If true the Karbala attack would mark one of the single deadliest attacks since anti-government protests erupted earlier this month.

In total at least 250 people have now been killed as the leaderless and largely spontaneous, rallies have been met with bullets and teargas.

A local journalist in Karbala told The Independent that protesters defied a curfew imposed by the local governor on Monday night and tried to enter a local government building.

Later, men wearing plain black uniforms attacked, firing teargas and live ammunition at the protesters by the government building before moving to Education Square and firing on the crowds there.

“They arrested scores of youth, activists and journalists, and then used live ammunition against them ... Police later removed banners and tents,” said the journalist, who asked not to be named for security reasons.

“University students, lawyers, syndicates’ officials, and activists returned to the square and many are still there despite the heavy security deployment,” he added.

The witness said that masked gunmen in black plain clothes arrived and started shooting at the protesters. Tents caught fire, igniting a blaze, he added.

Amnesty corroborated the accounts saying that security forces had charged at protesters with live ammunition and even attempted to run people over.

Doctors told Amnesty that protesters were being treated for shrapnel and gunshot wounds to legs, eyes, stomachs and heads.

“Security forces opened fire on the protesters they were chasing,” one witness told the rights group.

He added: “There was a black four-wheel drive that started to drive towards the roundabout and attempted to run over the protesters. It was complete horror. There were women and children. The children were screaming. The security forces dispersed everyone and started chasing them into the side streets.

Karbala’s police chief has denied that any protesters had been killed and said only one person had died in an unrelated criminal incident.

The police statement claimed footage of security forces shooting at protesters was fabricated and designed to “incite the street” in the city.

Local governor Nassif al-Khattabi echoed the denial, calling media reports of dozens of deaths “completely baseless”.

“The photos and videos of deaths that spread on social media websites are fabricated and part of the media campaign against the holy city,” he said during a news conference broadcast by state-owned Iraqia News TV.

This week marked the second wave of protests this month against prime minister Adel Abdul Mahdi’s government, deep-seated corruption, economic stagnation and terrible public services.

The demonstrations, which have gripped areas across the country including Baghdad, Karbala and cities in the south, first erupted at the start of October.

In Baghdad’s Tahrir Square local media reported that thousands of Iraqis defied a curfew which started at midnight Tuesday to go out and protest.

A teacher in the well-known rallying point told Reuters: “They threatened us with our jobs, said they would cut our salaries off if we came, they can keep the salaries! Why all this blood? Why have all these young men lost their lives?”

An Iraqi government committee investigated the first wave of rallies and found that 149 civilians were killed because security forces used excessive force and live fire to quell protests.

The report said more than 70 of the deaths were caused by shots to the head or chest and held senior commanders responsible but stopped short of blaming the prime minister.

The United Nations mission in Iraq has accused the Iraqi authorities of committing serious human rights violations and abuses in their handling of the unrest.

Amnesty said on Tuesday that Iraqi forces had “resorted to excessive and often lethal force” to disperse protesters in a “reckless and utterly unlawful manner”.

“Iraqi authorities must immediately rein in security forces to prevent further bloodshed. Iraqi forces must order an independent impartial investigation into events last night in Karbala and ensure all those responsible are held accountable for their actions,” Lynn Maalouf, Amnesty’s Middle East research director, said.

Karbala, a Shia shrine city, is home to the tombs of the saints Abbas and Hussein, a highly revered figure in both Iran and Iraq whose seventh-century death at the hands of the then caliph became a rallying cry against injustice.

Baghdad police use tear gas to disperse demonstrators

Politically well-connected Iranian firms have poured tens of millions of dollars in the shrine city of Karbala, building hotels and other businesses that facilitate the highly lucrative pilgrimages of millions of Shia from across the Middle East and south Asia.

Iranian officials have been worried about the weeks-long anti-government unrest in Karbala, according to a former official briefed on the matter, concerned protesters’ spirit of defiance could inspire uprisings in Iran.

The city of 700,000 about 60 miles south of Baghdad is home to seminaries that train religious scholars from the Middle East and south Asia, and is well-connected to scholastic institutions in the Iranian cities of Qom and Mashhad.

Mr Abdul Mahdi, who took office just one year ago, has promised reforms and ordered a broad reshuffle of the cabinet but that has failed to quell the unrest.

On Sunday a government spokesman warned that anyone disrupting work or skipping school would be severely punished.

Despite its vast oil wealth, Opec member Iraq suffers from soaring unemployment and crumbling infrastructure, with many households blighted by power cuts, as well as limited access to clean water and healthcare.

The unrest has shattered nearly two years of relative stability in Iraq, which was recovering from foreign occupation, civil war and an Islamic State insurgency between 2003 and 2017.