Iran fired rockets early on Wednesday at Iraq's al Asad airbase, which hosts US forces, hours after the funeral of an Iranian commander whose killing in a US drone strike has raised fears of a wider war in the Middle East.
Iranian news agency Mehr said Iran's Islamic Revolutionary Guard Corps had targeted the base. Tehran has vowed retaliation for the killing of Iranian military commander Qassem Soleimani.
It was not immediately clear what the extent of damage or casualties was at the base.
US President Donald Trump has been briefed on reports of an attack on US facilities in Iraq and was monitoring the situation, White House spokeswoman Stephanie Grisham said.
"We are aware of the reports of attacks on US facilities in Iraq. The president has been briefed and is monitoring the situation closely and consulting with his national security team," Grisham said in a statement.
Earlier on Tuesday, US Defense Secretary Mark Esper said the United States should anticipate retaliation from Iran over the killing in Iraq of Soleimani, commander of the elite Quds Force.
"I think we should expect that they will retaliate in some way, shape or form," Esper told a news briefing at the Pentagon, adding that such retaliation could be through Iran-backed proxy groups outside of Iran or "by their own hand."
"We're prepared for any contingency. And then we will respond appropriately to whatever they do."