A barrage of Katyusha rockets targeted an Iraqi air base that houses American troops south of the city of Mosul on Friday, two security officials said. There was no immediate word of casualties from the attack.
The rocket fire appears to have originated in Mosul and struck the Iraqi army base in Qayyara, about 60 kilometers (38 miles) south of Mosul, where a U.S.-led coalition is helping Iraqi forces battle remnants of the Islamic State group.
The Iraqi officials who spoke to The Associated Press did so on condition of anonymity under regulations.
There was no immediate claim of responsibility nor was it clear if any of the rockets struck the base.
Iraq announced victory over ISIS two years ago, but the extremist group is still active through sleeper cells and frequently mount attacks on Iraqi security forces.
Some hard-line Iraqi militias loyal to Iran have recently threatened to carry out attacks against Americans in the country. The U.S. maintains about 5,000 troops in Iraq.
American forces withdrew from Iraq in 2011 but returned in 2014 at the invitation of the government to help battle ISIS after it seized vast areas in the north and west of the country, including Iraq's second largest city, Mosul. A U.S.-led coalition provided crucial air support as Iraqi forces regrouped and drove IS out in a costly three-year campaign.
The attack on Friday came as large parts of Iraq, including the capital of Baghdad and Shiite-majority southern provinces, are engulfed in anti-government protests. Rockets have been fired near the U.S. Embassy in the heavily fortified Green Zone in the Iraqi capital on several occasions recently.
Mosul, which was largely destroyed during the war against the Islamic State group, lies north of Baghdad and has not seen any anti-government protests.