Three rockets initially fell in an area where US company Sallyport -- the contractor that maintains F-16 aircraft purchased by Iraq from the US -- is located, the security source said, requesting anonymity.

A foreign employee of Sallyport was lightly wounded, according to this source.

Three other rockets were fired around 15 minutes later, the source added, saying they fell near the base without hitting it.

Pentagon spokesperson Commander Jessica McNulty said no US or coalition troops were assigned at Balad, but noted that US citizen contractors worked there.

Citing initial reports, McNulty said there were no US casualties or damage.

It is the second attack targeting US interests in under 24 hours, after two rockets Sunday targeted an airbase at Baghdad airport housing US-led coalition troops. Sunday's attack did not cause casualties.

There was no immediate claim of responsibility for either attack.

Around 30 rocket or bomb attacks have targeted American interests in Iraq -- including troops, the embassy or Iraqi supply convoys to foreign forces -- since President Joe Biden took office in January.

Two foreign contractors, one Iraqi contractor and eight Iraqi civilians have been killed in the attacks.

Washington routinely blames Iran-linked Iraqi factions for such attacks on its troops and diplomats.

In early April, two rockets hit near Balad, without causing casualties or property damage.

Also last month, an explosives-packed drone slammed into Iraq's Arbil airport in the first reported use of such a weapon against a base used by US-led coalition troops in the country, according to officials.

Dozens of other attacks were carried out in Iraq from autumn 2019 during the administration of Biden's predecessor Donald Trump.

The operations are sometimes claimed by obscure groups that experts say are smokescreens for Iran-backed organisations long present in Iraq.

The strikes come at a sensitive time as Tehran is engaged in talks with world powers aimed at bringing the US back into a 2015 nuclear deal.

The agreement, which curbs Iran's nuclear programme in exchange for sanctions relief, has been on life support since Trump withdrew in 2018.

Pro-Iran Iraqi groups have vowed to ramp up attacks to force out the "occupying" US forces in recent months, sometimes against Tehran's wishes, according to some experts.

Baghdad last month reportedly hosted a secret meeting of senior officials from Tehran and US-ally Saudi Arabia.