Iranian aircraft conducted strikes against Islamic State positions in eastern Iraq last weekend, expanding Tehran’s role as a close ally of Iraq’s Shiite-led government.

“We do think they did do some airstrikes at targets in Iraq,” said a senior U.S. defense official, who added that “several” Iranian planes were involved. Although Iran has conducted surveillance flights in Iraq in recent months, the strikes would be the first confirmed air attacks.

“We’ve long said they have a presence in Iraq, contributing to helping the Iraqis against ISIL,” said the official, speaking on the condition of anonymity, given the sensitivity of the matter, and using an acronym for the militant group.

Jane’s Defense Weekly reported Monday that an Iranian F-4 Phantom II struck targets in the eastern Iraqi province of Diyala, near the Iranian border. The plane appeared on video shot Sunday by Al Jazeera, which Jane’s said erroneously identified it as an Iraqi aircraft. Only Iran and Turkey fly F-4s in the region, Jane’s said.

U.S. military spokesmen indirectly confirmed the reports Tuesday. “I have no reason to believe that they’re not true,” said the Pentagon’s press secretary, Rear Adm. John F. Kirby. But “you should consult the Iranian government to speak to the activities of their military,” he said.

It is unlikely that U.S. military officials coordinating the numerous American and European warplanes flying bombing missions over Iraq were unaware of the flights, although spokesmen said the U.S. military was not in contact with Iran.

“We maintain good situational awareness of the activity taking place in the airspace over Iraq and Syria in order to ensure reasonably safe and effective operations by our forces,” said Maj. Curtis J. Kellogg, a spokesman for the U.S. Central Command. “We coordinate our air operations in Iraq with Iraqi security forces. . . . We don’t coordinate our operations with Iran.”

Rafid Jaboori, a spokesman for the office of Iraqi Prime Minister Haider al-Abadi, declined to comment on whether Iranian jets had struck in Iraqi territory but said that Iran remains a key ally in the fight against the Islamic State. Iraq needs “the help of all its friends,” he said. He confirmed that Iran has military advisers in Iraq, “like the Americans do,” but would not discuss further details of their assistance.

In an interview Monday on Lebanese television, Abadi said that Iran had stood by Iraq and swiftly provided assistance early this year while Western nations initially hesitated, according to Iran’s English-language Press TV.

Members of Iran’s Revolutionary Guard Corps have been seen in Iraq with Shiite militia ground forces fighting the Islamic State, and Iran has provided weapons and other supplies to the Iraqi military and to Kurdish forces, called the peshmerga, operating in northern Iraq.

Qassem Soleimani, the head of Iran’s elite Quds Force, has visited Iraq frequently since about a third of the country’s territory fell into the hands of the Islamic State during the summer. Photographs showing the military commander in fatigues on the battlefield have circulated on social media. One image shows him hugging Hadi al-Ameri, the head of Iraq’s Badr Brigade, which is leading the fight in Diyala, the province where the Iranian strikes allegedly took place.

Ameri denied that Iranian jets had carried out raids in Iraq.

“There have never, ever been any Iranian strikes,” said the militia leader, who describes Soleimani as a “close friend.”

Iraq complained that it lacked the air power to fend off the Islamic State’s advances as the group began to make inroads at the start of the year. After the fall of Mosul in June, Iraq scrambled to cobble together an air force from second-hand aircraft — including Soviet-made Su-25 fighters sent from Iran. Analysts said the Su-25s would most likely need to be flown by Iranians because Iraq lacked qualified pilots.

Iran’s F-4 Phantom II jets were made by McDonnell Douglas and obtained prior to the Islamic Revolution in 1979.

The Iranian air attack took place in the eastern Iraqi town of Saadiya, northeast of Baghdad, Britain’s Telegraph newspaper reported. It said Al Jazeera’s video was taken during a key battle for the town, which became a major militant base after being taken over by the Islamic State in June. The area is also some distance from where U.S. airstrikes have taken place in Iraq.

Morris reported from Beirut. Missy Ryan in Washington contributed to this report.