Four bases used by the Hashed have been hit by mysterious explosions over the past month, but there have been no claims of responsibility or media access to the facilities.

On Wednesday, the Hashed said it had carried out its own investigation and pointed the finger at the US military.

"We announce that the first and last entity responsible for what happened are American forces, and we will hold them responsible for whatever happens from today onwards," the paramilitary group said in a statement.

The statement said the attacks were carried out by "agents or in special operations with modern air planes," but did not provide further details.

It did say its probe found US forces this year had allowed four Israeli drones to enter Iraqi airspace and "target Iraqi military headquarters," without explicitly accusing Israel of carrying out any attacks.

Formed in 2014 in response to the Islamic State jihadist group's sweep across Iraq, the Hashed is dominated by pro-Iran Shiite groups and is largely opposed to the US.

The string of incidents at Hashed bases began in mid-July, when an Iraqi fighter was killed and two Iranians were wounded in shelling on a base in Iraq's Amerli region by "an unidentified drone," according to a statement by the Iraqi joint operations command.

The Pentagon denied at the time that it was involved in that incident.

Contacted on Wednesday, the US-led coalition in Iraq declined to comment on the Hashed's accusations, referring AFP to the Iraqi government.

An estimated 5,200 US troops are in bases across Iraq in training and advisory roles.

Earlier this summer, a string of rocket attacks targeted several bases, sparking concern of a potential confrontation between the US and Iran on Iraqi soil.