Members of Iraq's Hashd al-Shaabi (Popular Mobilization Forces) paramilitaries march with the group's flags during a parade marking al-Quds (Jerusalem) International Day in the southern Iraqi city of Basra on May 31. (HUSSEIN FALEH/AFP/Getty Images)

Iranian-backed militias in Iraq warned Wednesday that foreign aircraft flying over the country may be treated as “hostile” amid growing suspicions that Israel is responsible for mysterious explosions at militia bases.

The warning came in a statement issued by Abu Mahdi al-Mohandes, the deputy commander of the powerful coalition of Shiite Muslim militias known as Hashd al-Shaabi, or Popular Mobilization Forces (PMF), which includes paramilitary groups that owe allegiance to Iran. 

The statement blamed Israeli drones for four big blasts at militia bases over the past month, all of them at warehouses storing ammunition and weapons, and accused the U.S. military of aiding the strikes by allowing Israel to use U.S. bases in Iraq.

“We have informed the Joint Operations Command that we will regard any foreign aircraft flying over our headquarters without the knowledge of the Iraqi government as hostile, and will deal with it accordingly,” the statement said.

The U.S. military responded by tweeting that it operates in Iraq at the request of the Iraqi government and complies with all Iraqi laws and directions. The only purpose for being in Iraq is “to enable our Iraqi Security Force partners in the mission of an enduring defeat of Daesh,” the military said, using the Arabic acronym for the Islamic State.

Israel has not confirmed or denied responsibility for the attacks, but during a visit to Ukraine this week, Prime Minister Benjamin Netanyahu appeared to hint at Israeli involvement, responding to a reporter’s question about whether it was behind the explosions by saying that “Iran has no immunity, anywhere.”

“We will act — and currently are acting — against them wherever it is necessary,” he said.

If confirmed, Israel’s involvement would suggest it has opened a new front in its ongoing fight to prevent Iranian-backed militias in the region from deploying sophisticated weapons capable of targeting Israel. The explosions at the militia bases in Iraq are reminiscent of those associated with scores of airstrikes conducted by Israel in Syria over the past five years, which mostly targeted missile storage sites or suspected transfers of weapons to the Lebanese Shiite Hezbollah movement.

Israeli airstrikes in Iraq could complicate the U.S. effort to combat a revived Islamic State insurgency there and risk drawing Iraq into escalating hostilities between the United States and Iran. 

The militia statement was the strongest indication to date that Iraqis suspect Israel is behind the explosions, including one Tuesday at a militia base near an air base at Balad, where U.S. forces maintain a presence.

After the first alleged strike, on July 19 at a Shiite base in the northeastern town of Amerli, the Iraqi army immediately said an “unidentified drone” was responsible. The PMF subsequently claimed an accident had occurred, while the government declined to assign blame pending an investigation.

Then came two more blasts at weapons warehouses, one at Camp Ashraf, a headquarters for the powerful Badr Organization in eastern Diyala province, and one last week at Camp Saqr south of Baghdad. The latter ignited a huge blaze, sending rockets and bullets exploding over densely populated neighborhoods for up to five hours.

Three days later, Iraqi Prime Minister Adel Abdul Mahdi ordered that storage facilities for weapons should be moved away from residential areas and also that all international flights over Iraq should receive advance government approval, the first indication that the government suspected foreign involvement. The U.S. military said it would comply with all Iraqi government requirements and that the order would not impact its ability to provide support for missions against the Islamic State.

One question is how Israel would be able to attack targets so far from its borders. Israel has not struck Iraq since a 1981 mission to bomb the Osirak nuclear reactor constructed by former president Saddam Hussein. 

One possibility would be that Israel was using its newest-model drones. Another would be that the strikes were carried out by recently acquired U.S.-made F-35 aircraft, according to a report Wednesday by the Middle East Institute.

“Israeli intelligence has known for more than a year that Iran had begun deploying sophisticated rocket and ballistic missile systems into Iraqi territory, some to be based there permanently, others to be dispatched by land to Syria and Lebanon,” the report added.

Mustafa Salim in Baghdad contributed to this report.