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, officials said Thursday.

There were no casualties in the strike on the capital of northern Iraq's autonomous Kurdish region late Wednesday, although it did cause damage to a building in the military part of the airport.

It comes after around 20 bomb and rocket attacks blamed on pro-Iran Shiite armed groups against facilities used by coalition troops or diplomats in Iraq since US President Joe Biden took office in January.

The attacks have mostly been claimed by shadowy Shiite armed groups aligned with Iran who is demanding that the Biden administration set a pullout date for Iraq as it has for Afghanistan. "A drone packed with TNT targeted a coalition base at Arbil airport," the Kurdish region's interior ministry said in a statement.

There was no immediate claim of responsibility for the attack, which caused an explosion heard across Arbil. But a shadowy pro-Iranian group calling itself Awliyaa al-Dam (Guardians of Blood), which claimed responsibility for a previous attack on the same airport in February, hailed the strike on the messaging app Telegram.

In the February attack, more than a dozen rockets targeted the military complex inside the airport, killing an Iraqi civilian and a foreign contractor working with US-led troops.

Washington -- which has promised to withdraw the troops it deployed in support of Baghdad's successful fightback against the Islamic State group but has refrained from setting a date -- said it was "outraged" by the latest violence,

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"The Iraqi people have suffered for far too long from this kind of violence and violation of their sovereignty," State Department spokesman Ned Price said on Twitter.

Iraq's President Barham Saleh, who is himself a Kurd, condemned the latest attack on the Kurdish regional capital and urged all Iraqis to unite against the "terrorists" behind it. "Once again, infrastructure has been targeted in Arbil as it has been before in Baghdad and elsewhere," he said. "These terrorist crimes... require us to unite behind the security forces to enforce the law on the terrorists."

'Dangerous Escalation'

Another leading Kurdish politician, ex-foreign minister Hoshyar Zebari, explicitly blamed pro-Iranian "militia" for the attack. "It seems the same militia who targeted the airport two months ago are at it again," Zebari said on Twitter. "This is a clear & dangerous escalation."

There has been mounting pressure on the Baghdad government from pro-Iran factions among Iraq's Shiite majority to impose a date for a US withdrawal.

Pro-Iran groups have been ratcheting up their rhetoric, vowing to ramp up attacks to force out the "occupying" US forces, and there have been almost daily attacks on coalition supply convoys across the mainly Shiite south.

Earlier Wednesday, two roadside bombs exploded as convoys passed through the southern provinces of Dhi Qar and Diwaniyah, security sources said.

The United States last week committed to withdrawing all remaining combat forces from Iraq, although the two countries did not set a timeline for what would be a second US withdrawal since the 2003 invasion which toppled Saddam Hussein.

The announcement came as the Biden administration resumed a "strategic dialogue" with the government of Prime Minister Mustafa al-Kadhemi, who is seen as too close to Washington by pro-Iranian groups.

Like other minority groups, Iraq's Kurds oppose any swift US withdrawal, seeing the coalition troop presence as protection against any repetition of the bloody jihadist incursions into Kurdish areas of 2014.

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