BEIRUT: The U.S.-led coalition destroyed three makeshift oil refineries in jihadist-controlled territory in Syria early Sunday as it pressed efforts to deny ISIS militants funding, an activist group said.

The coalition strikes hit close by the Turkish frontier, near the town of Tal Abyad just across the border fence from the Turkish town of Akcakale, the Syrian Observatory for Human Rights said.

They came after at least a dozen strikes on Thursday night on the refinery infrastructure that the jihadists have developed in the swath of territory they control in eastern Syria, which includes many of the country’s main oil fields.

“At least three makeshift refineries under IS control in the Tal Abyad region were destroyed overnight,” the Observatory said.

“IS had been refining crude and selling it to Turkish buyers,” said the Britain-based watchdog, which has a broad network of sources inside Syria.

Before the launch of U.S.-led air strikes on ISIS in Syria last Tuesday analysts say the jihadists were earning as much as $3 million a day from oil revenues.

Output from ISIS-controlled fields stood at 80,000 barrels per day, far exceeding the 17,000 barrels per day the Syrian oil ministry said it was pumping.

The strikes around Tal Abyad came after Saturday raids on the mainly Kurdish town of Ain al-Arab, also very close to the Turkish border.

The town, known as Kobani in Kurdish, has been under assault by ISIS for more than a week, sparking an exodus of at least 160,000 refugees into Turkey.

The coalition also kept up its raids on the jihadist heartland province of Raqqa early Sunday as it pressed what Washington says are “near continuous” strikes.

The raids destroyed a plastics factory outside Raqqa city, killing one civilian, the Observatory said.