An attack Wednesday at the airport of Irbil, capital of Iraqi Kurdistan, was carried out by drone, the Kurdish interior ministry said — an unprecedented escalation of the arms used to target U.S. soldiers based there.
"A drone charged with TNT targeted a coalition base at Irbil's airport," the ministry said, adding that no one was hurt in the blast but a building was damaged.
There was no immediate claim of responsibility for the attack, which caused a loud explosion heard across the city.
However, a shadowy pro-Iranian group, blamed for a similar attack in mid-February, hailed the blast in pro-Iran channels on the messaging app Telegram.
A security cordon blocked all access to the airport, witnesses reported. The governor said air links were not interrupted.
Some 20 bomb or rocket attacks have targeted bases housing U.S. soldiers or diplomats in Iraq since U.S. President Joe Biden took office at the end of January.
Dozens more took place during the preceding 18 months, with Washington consistently blaming pro-Iran armed factions.
Washington and Tehran are both allies of Baghdad but remain sharply at odds over Iran's nuclear program.
On February 15, more than a dozen rockets targeted a military complex inside Irbil airport, killing an Iraqi civilian and a foreign contractor working with U.S.-led troops.
The complex hosts foreign troops deployed as part of a U.S.-led coalition helping Iraq fight the Islamic State group, a fight that Baghdad declared as won in late 2017.
A shadowy group calling itself Awliyaa al-Dam (Guardians of Blood) claimed the February attack in Irbil and in a follow-up statement vowed to keep targeting U.S. forces in Iraq.
"It seems the same militia who targeted the airport two months ago are at it again," Iraq 's longtime former Foreign Minister Hoshyar Zebari, a prominent Kurdish political figure, posted on Twitter in an allusion to pro-Iranian factions.
Last October, hundreds of supporters of Hashed al-Shaabi, an Iraqi paramilitary network dominated by Iran-backed factions, set fire to the Baghdad headquarters of Zebari's party after he criticized them.
That did not stop Zebari from pointing the blame at pro-Iranian factions for Wednesday's attack, however. "This is a clear & dangerous escalation," he tweeted.
Pro-Iran groups have been ratcheting up their rhetoric, vowing to ramp up attacks to force out the "occupying" U.S. forces, more than a year after the Iraqi parliament voted to expel the American troops.
Counterterrorism officials said only one rocket hit the airport on this occasion.
But an Iraqi security source told AFP that other rockets had crashed in the vicinity, one of them targeting Turkish troops.
Earlier in the day, two bombs exploded on roads where Iraqi logistics convoys were carrying equipment for the international coalition in the southern provinces of Dhi Qar and Diwaniyah, according to security sources.
The United States last week committed to move all remaining combat forces from Iraq, although the two countries did not set a timeline in what would be the second withdrawal since the 2003 invasion.
The announcement came as the Biden administration resumed a "strategic dialogue" with the government of Prime Minister Mustafa al-Kadhimi, who is seen as too close to Washington by Iraq's powerful pro-Iranian factions.
The region of Kurdistan has been autonomous since 1991 and has a population of 5 million.