The rare and combative statement by the state-sanctioned militias known collectively as the Popular Mobilization Forces, or PMF, came in the wake of at least three mysterious explosions at PMF bases around Iraq over the past month. A government investigation, obtained by the Associated Press on Wednesday, found that one of the blasts, last week near Baghdad, was caused by a drone strike.
American officials denied the U.S. had any role in the explosions.
Asked about the mounting speculation that Israel was striking in Iraq, Israeli Prime Minister Benjamin Netanyahu on Monday struck his country's traditional stance of neither denying nor confirming such operations.
"Iran has no immunity, anywhere ... We will act - and currently are acting - against them, wherever it is necessary," he said during a visit to Ukraine, quoted in the Times of Israel.
If Israel did carry out the bombings, it would be an expansion of its campaign against Iran's spreading influence in the region. Israel is known to have struck Iranian targets in Syria on numerous occasions - as well as in Lebanon and Sudan in the past. But the last time Israel was known to have struck inside Iraq was in 1981, when Israeli fighter jets bombed an under-construction Iraqi nuclear reactor south of Baghdad.
The PMF's statement was the latest sign of Iraq's fragile government getting caught in the middle amid the tensions between Iran and the United States. Iran wields powerful influence over the Iraqi government through its support of the PMF militias, which were a major force in the fight against the Islamic State group.
At the same time, Iraq hosts American troops and forces belonging to the U.S. coalition fighting IS, which conduct frequent reconnaissance missions and occasional airstrikes.
There was no immediate comment from government officials to the PMF statement, which appears to have been issued without prior consultation with Iraqi security forces - an embarrassing sign of how the militias operate independently.
The PMF said in its statement that it had information that the U.S. brought four Israeli drones from Azerbaijan to Iraq "as part of the U.S. fleet" to carry out reconnaissance and targeting of militia positions.
It was not clear from the statement who the PMF was accusing of directly carrying out the attacks. But it said it holds the U.S. "ultimately responsible for what happened, and we will hold it responsible for what will happen as of today. We have no choice but to defend ourselves and our bases with the weapons at our disposal," said the statement, signed by Abu Mahdi al-Muhandis, the powerful deputy head of the PMF who once battled U.S. troops in Iraq.
The PMF warned it would consider any foreign aircraft flying over its bases without Iraqi government authorization to be "hostile aircraft that will be dealt with accordingly."
The most recent of the explosions at PMF positions came Tuesday night, at a munitions depot north of Baghdad. The deadliest, a July 19 blast, was blamed on a drone that hit a base in Amirli, northern Iraq, killing two Iranians and causing a huge fire.
A massive explosion on Aug. 12 at the al-Saqr military base near Baghdad shook the capital, destroyed several homes, killed one civilian and wounded 28 others. The base housed a weapons depot for the Iraqi federal police and the PMF.
A panel created by the government to investigate that blast ruled out earlier suggestions that it was caused by an electrical short circuit or faulty storage of munitions. Instead, it said it was caused by a drone strike, according to a copy of the panel's report obtained by the AP.
The report did not say who the drone belonged to.
Following a national security meeting last week to discuss the string of attacks, Iraqi Prime Minister Adel Abdul-Mahdi ordered a ban on all military flights throughout the country - including by members of the U.S.-led coalition in Iraq - unless specifically authorized by the Defense Ministry. The U.S. military's Central Command quickly said it would comply with that order as its forces are "guests within Iraq's sovereign borders."
The investigation report concluded that aircraft belonging to the coalition were in the skies around the time of the blast. It noted that Iraqi radar are not able to distinguish between coalition and other drones.
Asked to comment on that, a coalition spokesman referred the AP to the Iraqi government for questions about the investigation.
The series of blasts has sparked wide speculation among media and officials over who was behind them - with Israel, the United States, the Islamic State group or rival Iraqi factions all raised as possibilities. The Iraqi government has not formally addressed the reports.
Israel has long-range armed drones called Eitans capable of flying to targets in Iraq, some 1,000 kilometers (620 miles) away, and returning home.
Such long-range drones can be huge and visible on radar. But Iraqi air defenses could have mistaken them for permitted flights, since the airspace is full of fighting aircraft and drones flown by the U.S.
It's possible "any Eitans in Iraqi airspace were presumed to be coalition assets, which would explain why all coalition flights now need to be pre-approved by Baghdad," said Jeremy Binnie, the Middle East and Africa editor of Jane's Defence Weekly.
American officials told the AP the U.S. has no evidence or credible intelligence that Israel was behind the two most recent blasts - on Tuesday or on Aug. 12. They spoke on condition of anonymity because they were not authorized to speak about the issue. They also said the U.S. was not responsible for any of the strikes.
The CIA, however, also runs its own clandestine drone program separate from the U.S. military. The CIA declined to comment on the explosions.
Iraq already finds itself squeezed by tensions between Washington and Tehran over Iran's collapsing nuclear deal with world powers, brought on by President Donald Trump's unilaterally withdrawal of America from the accord over a year ago.
Associated Press writers Lolita C. Baldor in Washington, Jon Gambrell in Dubai, Zeina Karam in Beirut and Joseph Krauss in Jerusalem contributed to this report.
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