"Together, our governments will support the government of Iraq's investigation into the attacks to ensure that those responsible will be held accountable," they said.

The Western powers said they were "united" in the view "that attacks on US and Coalition personnel and facilities will not be tolerated and reiterate our steadfast commitment to the fight against ISIS".

An attack on Wednesday on an airport in Arbil, capital of Iraqi Kurdistan, was carried out by drone, according to the Kurdish interior ministry, in an unprecedented escalation of the arms used to target US soldiers based there.

No one was hurt in the blast but a building was damaged.

A Turkish soldier was killed by rocket fire at around the same time at a military base 50 kilometres (30 miles) east in Bashiqa, Ankara said, but there was no immediate confirmation of any link between the two attacks.

There was no immediate claim of responsibility for the airport drone attack.

But a shadowy pro-Iranian group calling itself Awliyaa al-Dam (Guardians of Blood), which claimed responsibility for a similar attack at the airport in February, hailed the blast in pro-Tehran channels on the messaging app Telegram.

Around 20 bomb or rocket attacks have targeted bases housing US soldiers or diplomats in Iraq since President Joe Biden took office at the end of January.

Dozens more took place over the preceding 18 months, with Washington consistently blaming pro-Iran factions.

Washington and Tehran are both allies of Baghdad, but remain sharply at odds over Iran's nuclear programme.

Pro-Iran groups have been ratcheting up their rhetoric, vowing to ramp up attacks to force out the "occupying" US forces, over a year after the Iraqi parliament voted to expel the American troops.

Washington last week committed to withdrawing all remaining combat forces from Iraq, although the two countries did not set a timeline for what would be the second withdrawal since the 2003 invasion.