Islamic State fighting positions and artillery were destroyed near the Beiji oil refinery in Iraq by coalition airstrikes, the U.S. Defense Department said.

The Islamic State at its peak was said to be generating about $2 million per day on pilfered oil. The militant group claimed a brief hold over the Beiji oil refinery north of Baghdad last year and heavy fighting has been reported recently in and around the area.

"Near Beiji, nine airstrikes struck two large and six smaller tactical units, destroyed two Islamic State fighting positions and an Islamic State heavy machine gun," the U.S. Department of Defense said Thursday.

The strikes come as Iraqi Prime Minister Haidar al-Abadi is in Washington discussing the fight against the terrorist group that at one point controlled large parts of Iraq and Syria.

A readout of a meeting between Abadi and Deputy Secretary of State Anthony Blinken said both sides reaffirmed their commitment to an "Iraq-led" effort to reclaim territory held by the Islamic State.

Washington last year said disrupting the ability of the Islamic State to raise funds through oil revenue was a key U.S. military objective.

Analysis from consultant group IHS last year found the Islamic State insurgency wasn't having much of an impact on the overall oil sector in Iraq. The Organization of Petroleum Exporting Countries said production from member-state Iraq was 3.6 million barrels of oil per day in March, a 9 percent increase from the previous month.