A senior US official on Monday said foreign elements were partially responsible for detaining hundreds of Iraqi protesters in a violent crackdown on anti-government demonstrations.
The official pointed to outsiders when asked about the rapid rise in the number of those detained and jailed in Iraq.
“We know what’s happening in all of these places with – I can’t say for sure who’s doing it, but they’re not all local, let’s just put it that way,” the official said.
Two human rights groups, the Euro-Mediterranean Human Rights Monitor and the Iraqi Warcrimes Documentation Centre, revealed this week that an armed Iraqi militia kidnapped at least 300 protesters from Baghdad’s Tahrir Square and was holding them in secret prisons.
Another report by Human Rights Watch suggested on Monday that the Iraqi government appeared to be complicit in a massacre committed against the protesters on December 6.
“Unidentified armed forces, apparently in co-operation with Iraqi national and local security forces, carried out a brutal spate of killings in Baghdad’s main protest area,” the organisation said.
“Estimates range between 29 and 80 dead, and 137 injured.”
It said 1,000 protesters were in Baghdad’s Khilani Square that night, 600 metres north of Tahrir Square, and in Senak Garage, a five-storey car park just off Khilani Square.
“Electricity to the area was cut during the attack police and military forces withdrew as the unidentified militia, some in uniforms, began shooting,” HRW said.
But Luay Al Khatteeb, Iraq's electricity minister, denied the report on Monday evening in a tweet.
"@hrw, check your facts! There was NO power shutdown but excessive damage to the power cables feeding street lighting in the area which was caused by direct shooting from unknown armed groups. This was documented by our staff and witnessed by protesters," he said.
More than 500 people have been killed in Iraq since the protests started in early October. The US has this month sanctioned Iraqi militia leaders who are close to Iran and are accused of heavy involvement in the crackdown.
"The US assesses that Iran is mobilising its transnational network of operatives in Iraq," Nicholas Heras, a senior fellow at the Centre for New American Security, told The National.
Mr Heras said this included militants with the Lebanese group Hezbollah, Iraqi militias, fighters from Afghanistan and Iranian agents.
“Iran has achieved a big enough force of operatives that they feel comfortable to apply them against Iraqis,” he said.
On Monday, the US called on Baghdad to "take actions" to protect US interests in the country after a series of attacks blamed on Tehran.
Since October 28, ten rocket attacks have targeted areas where US soldiers and diplomats are stationed.
They have not been claimed, but the United States has blamed Iranian-backed Shiite paramilitary groups.
US Defense Secretary Mark Esper told reporters he had expressed "concern about the optics in attacks on bases in Iraq where US troops and material might be," in a call with outgoing prime minister Adel Abdel Mahdi.
The US has "a right of self defense, that we would ask our Iraqi partners to take proactive actions... to get that under control, because it's not good for anybody," he told Mr Abdel Mahdi.