Iran has sent a small number of troops to help Iraq retake a major oil refinery from the Islamic State, the Associated Press reports. The Iranians will operate artillery and heavy weaponry in support of advancing Iraqi ground troops.

The move comes as the U.S.-led coalition air strikes against ISIS across the region continue, staging 22 strikes since Friday. From the AP:

Two US officials said Iranian forces had taken a significant offensive role in the Beiji operation in recent days, in conjunction with Iraqi Shia militia. The officials were not authorised to discuss the matter publicly and spoke on Friday on condition of anonymity.

One official said Iranians were operating artillery, 122mm rocket systems and surveillance and reconnaissance drones to help the Iraqi counteroffensive.

U.S. officials have not opposed Tehran-backed Shia militias’ involvement in the fight against ISIS so long as they operated under the command of the Iraqi government. Iran was previously accused of sending troops into Iraq to fight against ISIS in March.

Photo credit: AP Images. Contact the author of this post: brendan.oconnor@gawker.com.