The announcement came hours after another rocket attack targeted an Iraqi base where foreign troops are located, the 24th such attack in less than six months.

"The coalition is re-positioning troops from a few smaller bases," said coalition spokesman Myles Caggins.

The first redeployment was taking place Tuesday from Qaim, the western base along the border with Syria, a coalition official told AFP.

"A transfer ceremony is taking place today to hand over the facilities to Iraqi forces, and the intent is that all coalition troops will be leaving Qaim," the official said.

"It's historic," the official added, saying about 300 US-led coalition troops would be moved out of the base.

Some had already been redeployed to coalition positions in neighbouring war-ravaged Syria along with artillery, while others would be sent to other bases in Iraq or to Kuwait.

The official denied that the redeployment was a response to a spike over the last week in rocket attacks targeting foreign troops stationed across Iraq.

Early Tuesday, two Katyusha rockets hit an Iraqi base south of the capital hosting Spanish units of the US-led coalition as well as NATO troops.

On March 11, a volley of rockets killed two US military personnel and a British soldier at the Taji airbase, which was hit again three days later.

The US responded with air strikes on five positions controlled by Kataeb Hezbollah, a Iran-backed group and member of the Hashed al-Shaabi military network.

The Hashed has been formally integrated into the Iraqi state's security forces but more hardline groups continue to operate independently.

Some 5,200 US forces are positioned across Iraq and form the bulk of the coalition set up in 2014 to help local forces battle the Islamic State jihadist group.

They are deployed at about a dozen bases in Iraq alongside local forces.

A US official told AFP that coalition troops would leave three bases. In addition to Qaim, troops at the Qayyarah and Kirkuk bases in northern Iraq were set to be withdrawn by the end of April.

While Qaim has not been hit by rockets, both Qayyarah and Kirkuk have faced heavy rocket fire in recent months.

"There was no trigger but the violence helped keep the (withdrawal) pace fast," the official added, saying overall troop numbers in Iraq would remain the same.

In January, Iraq's parliament voted to oust all foreign forces from the country after a US drone strike in Baghdad killed top Iranian general Qasem Soleimani and the Hashed's deputy chief, Abu Mahdi al-Muhandis.