US-led warplanes have struck four refineries controlled by the Islamic State group in Syria, the Pentagon says, in a fresh wave of strikes that also hit targets in Iraq.
The United States, along with coalition partners Saudi Arabia and the United Arab Emirates, hit the four modular refineries as well as an IS command and control node which were all north of Raqa, US Central Command said in a statement on Sunday.
"Although we continue to assess the outcome of these attacks, initial indications are that they were successful," the statement said.
The air strikes against oil refineries are aimed at denying funding to the IS group, which has seized control over a swathe of territory straddling northwestern Iraq and eastern Syria, that includes most of Syria's main oil fields.
The jihadists have sought to exploit the oil fields through improvised refining and smuggling, and analysts said that before the launch of US-led air strikes on IS, the jihadists were earning as much as $US3 million ($A3.25 million) a day from oil revenues.
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The US-led strikes also destroyed a tank and damaged another near Deir Ezzor in eastern Syria, as well as three more armed vehicles and a Humvee in the northeast.
In Iraq, a safehouse near Baghdad was destroyed and a checkpoint damaged.
"Three air strikes near Fallujah destroyed two ISIL checkpoints and an ISIL transport vehicle," the statement added, using an alternate acronym for the IS group.
The United States and Arab allies launched air strikes against IS in northern and eastern Syria on Tuesday, more than a month after Washington began its air war on the jihadists in Iraq.
