US prepares to pull contractors from Iraq base following rocket attacks

Contractors have been withdrawn from a military base close to Baghdad following a series of attacks on American targets in Iraq, possibly related to rising tensions between Iran and the US in the Gulf.

Iraqi military sources told Reuters that hundreds of Lockheed Martin Corp and Sallyport Global workers were being immediately withdrawn from Balad military base, around 80km north of Baghdad, which was targeted by militants earlier this week.

It total, 400 contractors will be leaving "imminently" from the two bases due to "potential security threats", the sources added, saying that the evacuation will take place in two stages over ten days.

"Americans informed us that they will only keep limited, necessary staff who work closely on the maintenance of Iraqi F-16 war planes," the sources told the news agency.

Three bases hosting American soldiers or contractors have been hit by mortar shells and rockets this week, which comes amid a major rift between Iran and the US, centered on the Stait of Hormuz.

No group has claimed responsibity for the attacks, but Iranian-linked Iraqi militias are active in the country, some of which are hostile to the US.

Iraqi militias were key to the Baghdad government's battle against the Islamic State group, a campaign which the US supported with airstrikes, although it did not officially provide support to Shia armed groups.

Many are the remnants of the same Shia militias that fought a bloody war with American troops following the US-led invasion of Iraq in 2003.

IS still continue to carry out attacks on Iraqi forces and civilians, including a deadly bombing targeting a Shia mosque in Baghdad on Friday.