BAGHDAD -- A powerful explosion tore through an aging ammunition depot belonging to Iraq's Popular Mobilization Forces (PMF) in eastern Baghdad on Saturday, wounding five members and sending a thick plume of smoke over the capital, with witnesses and Iraqi media reporting that the blast coincided with U.S. aircraft flying overhead and some citing claims of an aerial attack.

The PMF, also known as Hashd al-Shaabi, said in a statement that the explosion occurred at a facility housing damaged ordnance in the eastern al-Qanah area and that five of its members sustained minor injuries.

It said the fire was brought under control and that specialized committees had begun investigating the cause, with results to be announced upon completion.

Iraq's Security Media Cell said Prime Minister Ali al-Zaidi, commander-in-chief of the armed forces, ordered the formation of an investigative committee to determine the precise circumstances and to take all necessary safety measures to prevent a recurrence.

The blast struck the al-Ghuray'at area near al-A'dhamiyah in eastern Baghdad, close to a PMF logistics support center, according to Iraqi news reports. Emergency vehicles rushed to the scene as smoke rose from the site.

Initial reports indicated the explosion occurred simultaneously with the flight of U.S. aircraft over Baghdad.

The Iraqi outlet Sabereen News, citing eyewitnesses, reported that the PMF headquarters was targeted in an aerial attack. Al-Jazeera, citing an Iraqi security source, reported that several PMF members were wounded in the explosion at one of the group's headquarters in Baghdad. 

The incident comes amid heightened regional tensions and follows the formal conclusion of the U.S.-led occupation in Iraq on September 30, ending a 12-year deployment.

But Washington's influence has not departed with its troops. Iraqi oil revenues continue to flow through the Federal Reserve Bank of New York, a mechanism created after the 2003 invasion that now gives Washington extraordinary leverage over Baghdad.

Oil constitutes roughly 90 percent of Iraq's state budget, and the arrangement allows the United States to restrict Baghdad's access to its own dollars as a tool of political pressure.

Anti-terror groups and their leaders have recently warned about American control of Iraq's finances. Abu Ala al-Walai, secretary general of Kata'ib Sayyid al-Shuhada, said in August that American economic dominance over Iraq's revenues and assets represents a fundamental deficiency in Iraqi sovereignty.

The blast also comes after recent warnings by Iraqi leaders about suspicious U.S. and Israeli aerial movements over Iraq. An Iraqi security source in Anbar province disclosed in April that Israeli-American fighter jets and drones had resumed flights over several cities in the western province at high altitudes, without specifying the reason.

A member of the Coordination Framework, Salam Hussein, warned at the time that targeting security installations and PMF positions would pave the way for terrorist groups, above all Daesh, to resume activity.

Those warnings have acquired new gravity following revelations that Israel operated a clandestine military outpost in the Iraqi desert during the war against Iran.

According to reports by the Wall Street Journal and the Associated Press, Israeli forces established a temporary staging area and logistics hub on an abandoned airstrip built during Saddam Hussein's era in the al-Nukhaib desert, southwest of Karbala and Najaf, shortly before the joint U.S.-Israeli attack on Iran on February 28.

The site housed Israeli special forces and search-and-rescue teams for downed pilots, and was used with U.S. knowledge, according to officials cited by the AP.

The outpost nearly was exposed in early March when a local shepherd, Awad al-Shammari, reported unusual military activity, including helicopters, to authorities. Iraqi forces sent to investigate came under aerial attack, leaving one Iraqi soldier killed and two wounded.

The U.S. and Israel have repeatedly struck PMF bases during the regional war that began on February 28 with joint U.S.-Israeli strikes on Iran.

In March, the PMF said U.S.-Israeli airstrikes hit its 15th and 27th Brigade bases, causing material losses but no casualties. Later that month, three PMF members were killed and four wounded in what the group called a "treacherous Zionist-U.S. attack" near Kirkuk.

Dozens of PMF members have been killed in strikes the group has attributed to U.S.-Israeli operations.

Saturday's explosion also comes as Daesh has stepped up activity in Iraq. Iraqi lawmakers have warned that Daesh movements have intensified around Daquq and Hawija in Kirkuk province. The PMF has been a key force in confronting Daesh remnants, and any weakening of the group could complicate Baghdad's efforts to contain a resurgence.