"At 9:30 pm (1830 GMT)... forces from the 47th brigade within Hashed al-Shaabi were hit by an explosion" in Babylon province, said the Hashed al-Shaabi alliance of former pro-Iran paramilitary groups now integrated into the regular army and repeatedly targeted by the US forces.

Several people were killed and wounded, said the alliance, whose name means Popular Mobilization Forces (PMF).

"Available information suggests that two patrols... were targeted with missiles fired from drones", the Hashed said in a second statement.

An official from the alliance told AFP that "four people were killed and others were critically wounded in blasts that hit a base belonging to the Hashed al-Shaabi".

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

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

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 -- largely halted in recent months -- against US forces in Iraq and neighbouring Syria.

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.

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, US 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 responsibility for 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.

Baghdad has sought to defuse tensions, engaging in talks with Washington on the future of the US-led coalition's mission in Iraq. Iran-backed groups have demanded a withdrawal.

The US military has around 2,500 troops in Iraq and 900 in Syria with an international coalition.

The coalition was deployed to Iraq at the government's request in 2014 to help combat the Islamic State group, which had taken over vast swathes of Iraq and neighbouring Syria.