A US contractor was killed, and another contractor and five US service personnel wounded, when a kamikaze drone "of Iranian origin" struck a maintenance facility on a base of the US-led coalition near Hasakeh in northeastern Syria, the Pentagon said.

In response, US Defense Secretary Lloyd Austin said Thursday that, at President Joe Biden's direction, he had ordered "precision air strikes tonight in eastern Syria against facilities used by groups affiliated with Iran's Islamic Revolutionary Guard Corps".

"The air strikes were conducted in response to today's attack as well as a series of recent attacks against coalition forces in Syria by groups affiliated with the IRGC," Austin said.

Hours later, 10 rockets were fired at US and coalition forces at the Green Village base at the Al-Omar oil field in northeast Syria, the US Central Command (CentCom) said.

There were no coalition injuries or damages to facilities at the base, but one rocket struck a home around five kilometers away, causing minor injuries to two women and two children, CentCom said

- Iran link -

The Pentagon blamed the initial drone attack on militias affiliated with Iran's Islamic Revolutionary Guard Corps.

The militias have a heavy presence across Syria, especially around the border with Iraq, and south and west of the Euphrates in Deir Ezzor province, where the latest US strikes took place.

The United States deploys about 900 troops in posts across northeastern Syria to keep pressure on the remnants of the Islamic State group and support the Kurdish-led Syrian Democratic Forces, which control most of the northeast.

The Pentagon said two F-15 fighters launched the retaliatory attack in the early morning hours local time. According to the Syrian Observatory for Human Rights, a Britain-based monitor with a wide network of sources on the ground, the US attack killed six fighters at a weapons depot inside Deir Ezzor city, killing six pro-Iran fighters, two near Al-Mayadeen, and six others near Albu Kamal.

Pentagon Spokesman Pat Ryder said the US air strikes were to protect US personnel.

"The strikes that we took last night were intended to send a very clear message that we will take the protection of our personnel seriously and that we will respond quickly and decisively if they are threatened," he said.

The strikes were "proportionate and deliberate action intended to limit the risk of escalation to minimise casualties," he said.

- 'Always respond' -

US personnel in Syria have frequently been targeted in attacks by militia groups the United States says are backed by Tehran.

Two of the US service members wounded on Thursday were treated on site, while the three other troops and one US contractor were evacuated to Iraq, the Pentagon said.

"We will always take all necessary measures to defend our people and will always respond at a time and place of our choosing," said CentCom chief General Michael Kurilla.

In January, the US military said three one-way attack drones were launched against the Al-Tanf garrison in Syria, with one breaching its air defences and wounding two allied Syrian fighters.

Last August, Biden ordered similar retaliatory strikes in Deir Ezzor province after several drones targeted a coalition outpost, without causing any casualties.

"We know that these groups are sponsored by Iran," Ryder said.

"So Iran certainly plays a role in terms of ensuring that this type of activity doesn't happen," he said.