The attack struck a position held by Brigade 45, a Hashed al-Shaabi unit based about 15 kilometres (10 miles) from Iraq's western desertic border with neighbouring Syria.

"As part of the string of Zionist attacks on Iraq, the evil Israeli crows have returned to target the Hashed al-Shaabi, this time with two drones inside Iraqi territory," the statement said.

It said one fighter was killed and another heavily wounded, revising an earlier toll of two dead.

"This blatant attack came with air cover over the area from American planes, in addition to a large balloon to monitor the area near the site of the incident," the statement added.

The attack is the latest in a string of blasts and drone sightings at Hashed bases across the country that have sparked concern of a possible proxy war between Iran, the US and Israel on Iraqi soil -- or in its airspace.

Explosions have been reported at four other Hashed bases since mid-July, and a fifth unit near Baghdad said on Thursday it shot at a surveillance drone flying over its position.

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.

The Hashed was established in 2014 from disparate armed groups and volunteers to fight back the Islamic State group.

The group has received training and other support from Iran, and the US and Israel are concerned the force acts an extension of their arch-foe.