Six rockets were fired on Friday at the Iraqi capital's airport, causing damage but no casualties, security sources said, the latest in a string of attacks the US blames on Iran-linked militias.

The rockets hit Baghdad International Airport's runways or parking areas, a source at the interior ministry said, noting that a “civilian plane has been hit and damaged”.

The attack was not immediately claimed.

A second security source confirmed the attack consisted of six rockets that fell around civil installations at the airport, damaging a plane, while a third source identified the plane as a Boeing 767 belonging to state-owned Iraqi Airways.

Iraqi Airways posted on its social media pages pictures of the damage, consisting of a hole near the nose of the plane that was out of service and stationary at the time of impact. No flights were affected by the attack, the airline added.

Recent months have seen rocket and drone attacks target the US embassy in Baghdad's high-security Green Zone, a US diplomatic facility at the airport and troops belonging to a US-led coalition stationed at Iraqi bases.

The attacks are rarely claimed but are routinely pinned on pro-Iran factions, who demand that US troops who were deployed to help Iraqi forces fight the militant Islamic State (IS) group leave the country.

The past few weeks have also seen violence targeting Iraqi politicians and parties, largely consisting of grenade attacks, but also extending to one rocket assault near the home of a key politician, amid tensions surrounding the formation of a new government.

Post-election tensions

The US-led coalition ended its combat mission in Iraq in December, four years after the Baghdad government declared victory over the IS.

But roughly 2,500 American soldiers and 1,000 coalition soldiers will remain deployed in Iraq to offer training, advice and assistance to national forces.

On January 3, US forces downed two armed drones that targeted the coalition at Baghdad airport, according to a coalition source.

On January 13, three people, including two children, were wounded by a rocket that hit a school in the Green Zone, while two other rockets fell inside the US embassy complex, without causing casualties.

In September, an “armed drone” attack targeted Arbil international airport in northern Iraq's Kurdistan region, where a base hosts coalition troops.

The more recent rocket and drone fire come amid a tense domestic political situation.

An election in October saw Fatah (Conquest) Alliance, the political wing of pro-Iran ex-paramilitary coalition Hashed al-Shaabi, lose most of its seats. It alleged the polls were rigged.

A bloc led by Shia cleric Moqtada Sadr, who once led an anti-US militia and who opposes all foreign interference, took the largest share of seats, and is trying to form a coalition government that could include Sunni and Kurdish factions.

Three rockets on Tuesday hit near the home of Sunni parliament speaker and prospective Sadr ally Mohammed al-Halbussi, just hours after the supreme court approved his re-election in that role.