The United States and partner nations conducted airstrikes against ISIS-held oil refineries on Saturday and Sunday, as part of a series of twelve strikes in Syria and Iraq, according to U.S. Central Command. Four modular oil refineries in Ar Raqqah, Syria, were targeted, Central Command said in a statement. "Although we continue to assess the outcome of these attacks, initial indications are that they were successful," the CentCom statement said.

"Our building was shaking and we saw fire, some 60 meters (65 yards) high, coming from the refinery," a local businessman, Mehmet Ozer, told The Associated Press. Strikes on the oil refineries aim at degrading ISIS' finances. The terror group earns an estimated $3 million a day from the refineries, according to the AP.

The weekend airstrikes also destroyed ISIS armed vehicles and Humvees in Syria, and an ISIS safe house and checkpoints in Iraq, according to Central Command. "All aircraft departed the strike areas safely," Central Command said. Saudi Arabia and the United Arab Emirates also participated in the strikes, according to Central Command. Three other Arab allies are also taking part in aerial campaigns against ISIS, and some European countries — including France, the Netherlands, Denmark, Belgium and Britain — are also assisting to combat the terror group.

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U.S. military will cont. to conduct targeted airstrikes against ISIL in #Syria and #Iraq as local forces go on the offensive against #ISIL — U.S. Dept of Defense (@DeptofDefense) September 28, 2014

— Courtney Kube and Elisha Fieldstadt, with The Associated Press