A monitoring group says the latest round of US air strikes on Islamic State in Syria have killed 14 of the group's militants.
Five civilians are also reported to have died in the raids.
Saudi Arabia and the United Arab Emirates joined the operation to destroy oil refineries in eastern Syria which are capable of producing millions of dollars' worth of revenue for the group.
A mix of manned and remotely-piloted aircraft were used to target oil production facilities near Al Mayadin, Al Hasakah and Abu Kamal.
A statement released by US Central Command said, "these small-scale refineries provided fuel to Isil (Islamic State) operations, money to finance their continued attacks throughout Iraq and Syria, and an economic asset to support their future operations.
"The US conducted these strikes as part of the President's comprehensive strategy to degrade and ultimately destroy Isil. The US and partner nations will continue to conduct airstrikes against Isil in Syria and Iraq and support Iraqi forces as they go on the offensive against this terrorist group."
But Syrian Kurds who fled towns and cities overrun by Islamic State said the group had responded to the airstrikes by focusing its assault near Syria's border with Turkey.
Despite the coalition's military superiority, an intensifying advance by IS militants on the northern town of Kobani underscored the difficulty Washington faces using airpower alone.
"Those airstrikes are not important. We need soldiers on the ground," said Hamed, a refugee who fled into Turkey from Islamic State.
British involvement
Overnight, the British Prime Minister David Cameron told the UN in New York that Britain was ready to join the military operation against IS - subject to his parliament approving the action when it's recalled tomorrow.
Addressing the UN General Assembly in New York, the Prime Minister said the militant group's rapid advance could be tackled with help from Iran and an end to Bashar al Assad's regime in Syria.
Mr Cameron was speaking ahead of an emergency debate in Parliament on Friday where he is expected to win cross-party support for airstrikes against IS targets in Iraq.
MPs will vote on whether RAF planes should join the US, France and five Arab states in bombing IS positions, possibly by the weekend.
Labour and the Liberal Democrats pledged their support after a formal request for assistance from Iraqi Prime Minister Haider Abadi put potential UK involvement on a legal footing.
The Prime Minister insisted Britain had learned from "past mistakes" in Afghanistan and Iraq, but they would not become an excuse for inaction.
"Isil is not a problem restricted to just one region. It has murderous plans to expand its borders well beyond Iraq and Syria and to carry out terrorist atrocities right across the world," he said.
