"The toll has now risen to four members of Hashed killed," said the official from the Hashed al-Shaabi alliance of pro-Iranian former paramilitary groups now integrated into the regular army.

He added that the blasts were caused by an "airstrike -- four or five missiles hit the base".

The security source confirmed that four people were killed, adding that the death toll was expected to rise.

On July 18, an explosion hit "logistics" warehouses belonging to Hashed south of Baghdad, and in April, one person was killed and eight wounded in a blast at a military base housing Hashed groups in Babylon province.

Hashed al-Shaabi is an integral part of the Iraqi security apparatus under the authority of the prime minister.

It includes some pro-Iran groups that have carried out dozens of attacks against US forces in Iraq and neighbouring Syria.

But those groups were also repeatedly targeted by the US forces.

The latest blasts comes after two drones were launched last week against an Iraqi base used by US-led troops without causing any damage.

For more than three months, as regional tensions soared over the Israel-Hamas war in Gaza, United States troops were targeted by rockets and drones more than 175 times in the Middle East, mainly in Iraq and Syria.

The Islamic Resistance of Iraq, a loose alliance of Iran-backed groups, claimed the majority of the attacks, saying they were in solidarity with Gaza Palestinians.

In January, a drone strike blamed on those groups killed three US soldiers in a base in Jordan. In retaliation, US forces launched dozens of strikes against Tehran-backed fighters.

Since then, attacks against US troops have largely halted.