 -- United States and Arab coalition warplanes conducted another round of airstrikes inside Syria today, this time targeting ISIS' lucrative oil production facilities. The terror group has used illicit oil sales as a means of funding its operations.

"I can confirm that U.S. military and Arab partner forces are undertaking additional strikes today against ISIL terrorists in Syria,” said Pentagon spokesman Rear Adm. John Kirby using another acronym for ISIS.

Kirby told ABC News that 12 targets were hit in Wednesday’s strikes focusing on modular oil refineries. He said the targets were located in a remote areas of eastern Syria.

In a statement U.S. Central Command said the strikes were conducted by fighters from the U.S., Saudi Arabia and the United Arab Emirates. American drones also participated in the strikes.

ISIS is said to be one of the most well-funded terrorist groups ever because it is generating its own funds through the illicit sale of oil from seized oil fields inside Syria. Kirby said the the strikes were intended to hit ISIS financially.

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“The destruction and degradation of these targets further limits ISIL's ability to lead, control, project power and conduct operations,” said the Centcom statement.

Centcom said the refineries produce an estimated 300 to 500 barrels of refined oil a day that generate as much as $2 million a day for ISIS.

Earlier Wednesday American fighters carried out an airstrike targeting eight ISIS vehicles on the Syrian side of the border with Iraq. An additional four airstrikes were carried out inside Iraq, near Erbil and outside of Baghdad. A U.S. official told ABC News that Jordanian aircraft conducted a separate strike inside Syria.

The new wave of airstrikes launched Wednesday night reflect how the U.S. air campaign over Syria will be a mix of planned strikes and targets of opportunity.

Pentagon spokesman Col. Steve Warren told reporters Wednesday “You’ll see a mix of what we’ve seen in Iraq the last several weeks, the result of active ISR that are armed.” ISR refers Intelligence, surveillance and reconnaissance aircraft – both manned and unmanned flying that are flying over Iraq and Syria.

“We’ll strike targets of opportunity when present,” said Warren. “ISR will allow us to develop more stationary targets we can strike when we choose.”

“I think you’re going to see a mix in coming days of both,” said Warren.

Warren said he could not confirm reports that the Khorasan Group’s leader was killed in the Monday airstrikes conducted near Aleppo. He would only say that overall the airstrikes were effective targeting facilities to degrade ISIS operations in both Syria and Iraq. He noted that there was no specific targeting undertaken in Monday’s airstrikes, but command and control centers were targeted and its possible leaders may have been in those facilities.

He characterized the airstrikes as effective and that as far as he knew there had been no civilian casualties in the strikes though they can’t be a hundred percent certain given that they don’t. “These strikes were very precise, we took all available mitigating actions to reduce civilian casualties and now we believe there were no civilian casualties,” Warren said.