U.S. officials said there is no information yet on any damage or casualties from the rockets.
Iran's Revolutionary Guards launched a missile attack on the Ain al-Assad and Erbil airbases Wednesday in Iraq, which hosts both Iraqi and United States forces.
"We warn all allied countries of the U.S. that if attacks are launched from bases in their countries on Iran, they will be a target of military retaliation," IRGC's statement reads which also said that Operation Martyr Soleimani tens of ground-to-ground missiles were fired at the base.
The Pentagon has now confirmed that these were surface-to-surface ballistic missile attacks.
Reuters, citing a U.S. official, said there is no information yet on any damage or casualties from the rockets. Sirens have been heard in total alert activated, as U.S. helicopters fly over the airbase.
Reports on the situation say anywhere between 12 to 35 rockets were fired at the base. While Iran's Fars news agency confirmed the attack dubbing it as the "start of Iran's vengeful U.S. retaliation" over the assassination of Major-General Qassem Soleimani on Jan. 2.
Later on Tuesday night, Iran's Minister of Foreign Affairs Javad Zarif said on Twitter that "Iran took and concluded proportionate measures in self-defense under Article 51 of U.N. Charter," adding that the country "does not seek escalation nor war, but will defend ourselves against any aggression."
Soleimani, head of the elite Quds Force, and Iraqi militia commander Abu Mahdi al-Muhandis were killed in an airstrike on their convoy in Baghdad airport, soon after Iran's government pledged it would avenge the deaths.
Ain Assad airbase is located in Iraq’s western Anbar province. It was first used by U.S. forces after the 2003 U.S.-led invasion that toppled Saddam Hussein. It later saw U.S. troops stationed there amid the fight against the Islamic State group in Iraq and Syria, as part of the U.S. occupation forces in Iraq.