The deaths come after a month of mysterious blasts at Hashed al-Shaabi arms depots and training camps that some of the force's top officials blamed on the US.

"Two unidentified drones targeted a Brigade 45 position belonging to the Hashed al-Shaabi in the Anbar district, 15 kilometres (10 miles) from the Iraqi-Syrian border," the statement said.

The attack "killed two fighters from the unit, wounded another and burned two vehicles," it added.

The statement did not accuse any particular force and there was no immediate claim of responsibility.

The Hashed was established from disparate armed groups and volunteers that united to fight back the Islamic State group's sweep across a third of Iraq in 2014.

The network is mostly Shiite and has received Iranian training, but it operates officially under Iraq's armed forces and uses military unit names.

Brigade 45 is one of several units made up of Kataib Hezbollah fighters, designated by the US as a "foreign terrorist organisation".

A military source from Kataib Hezbollah told AFP that one of the dead, Abu Ali al-Dabi, was a member of the unit's rocket squad.

"He fought in Syria and was previously detained by the Americans," the source said.

Over the last month, a string of suspicious explosions and drone sightings at Hashed bases have sparked concerns that escalating tensions between the US, Israel and Iran are boiling over into Iraq.

Hashed chief and Iraqi National Security Adviser Faleh al-Fayyadh has said preliminary investigations found the incidents were premeditated but had not yet revealed the perpetrators.

Deputy Hashed leader Abu Mehdi al-Muhandis, whom analysts say holds the real reins in the Hashed, has been unequivocal in blaming Washington.

On Thursday, Kataib Hezbollah issued a "final warning" to the US over the purported attacks.

"We issue a final warning to the American enemy that any new targeting of any Iraqi positions will be met with a tough, categorical response," it said in a statement.

The Pentagon has denied involvement, and US officials have told the New York Times that Israel has carried out multiple strikes in Iraq this month.

Israel has not claimed responsibility but Prime Minister Benjamin Netanyahu hinted at involvement last week, saying his country would "act against (Iran) whenever necessary".

One of Israel's biggest security concerns is the possibility that Iran could transfer rockets by land to its allies in Iraq, Syria and Lebanon that could then be used to attack the Jewish state.

To prevent such arms transfers, Israel has carried out several hundred strikes against Iranian forces and their allies in neighbouring Syria.

On Sunday, the head of Lebanon's powerful Hezbollah movement said Israel was behind a drone attack on the group's stronghold in a southern suburb of Beirut.

ac/mjg/dco

THE NEW YORK TIMES COMPANY