Frame grab shows airstrikes carried out by Russian air force near Raqqa.

ISIS militants on Thursday received heavy air strikes from the U.S.-led coalition and Russia in the same day, leaving their oil facility in eastern Syria destroyed and their bastion in the city of Raqqa bombarded by warplanes.

Warplanes bombed Raqqa, stronghold of ISIS insurgents, hitting some of the group’s offices and killing at least four civilians in the vicinity, residents and a monitor group said.

A resident in the city told Reuters there were at least 17 air strikes on the heart of Raqqa, and electricity had gone off in the city.

The UK-based Syrian Observatory for Human Rights, which monitors Syria’s civil war through a wide network of sources inside the country, said the air strikes hit several locations used by ISIS, including the perimeter of Raqqa’s Governorate building.

At least four civilians were killed, it said.

Who bombed Raqqa?

It was not immediately clear who bombed Raqqa, which in the past few months has been targeted by a U.S.-led air strike coalition and by Russians and Syrian government warplanes.

Oil facility destroyed

Meanwhile, air strikes by the U.S.-led coalition destroyed an oil facility run by ISIS near the city of Deir Ezzor, AFP quoted a spokesman as saying on Thursday.

The series of strikes late Wednesday on the Omar oil field near the city of Deir Ezzor would affect the jihadist organization’s ability to generate funds through oil sales, he said.

“There were strikes last night that struck Daesh-controlled oil refineries, command and control centres and transportation nodes” in the Omar oil field, U.S. operations officer Major Michael Filanowski told reporters in Baghdad.

“There were 26 targets and all 26 were struck,” he said. “That will impact their strategic ability to generate money.”

Oil makes $1.7 mln profit for ISIS

He said the amount of money ISIS was estimated to generate through its exploitation of the Omar oil field was between $1.7 million and $5.1 million a month.

The Syrian Observatory for Human Rights monitor said a coalition air raid on the Omar field destroyed pipelines and oil storage facilities.

Observatory chief Rami Abdel Rahman said the strike killed a civilian, and wounded several other civilians and ISIS fighters.

ISIS, which controls large regions of Syria and Iraq, has relied heavily on oil production to finance its self-proclaimed “caliphate”.

Russia destroys ISIS supply route

Russia’s military also carried out an air strike on a bridge over the Euphrates River in Syria which was being used by ISIS militants to bring supplies from Iraq into Syria, Russia’s RIA news agency quoted a defence ministry official as saying.

The official, Colonel-General Andrei Kartapolov, said the bridge was now impassable, the agency reported.

Russia’s military carried out an air strike on a bridge over the Euphrates River in Syria which was being used by ISIS militants to bring supplies from Iraq into Syria, Russia’s RIA news agency quoted a defence ministry official as saying.

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