The US-led coalition has targeted oil refineries in Syria during a third night of air strikes against Islamic State (IS) militants.
The raids – carried out by US, Saudi and UAE aircraft – killed 14 IS fighters and five civilians in eastern Syria, activists said.
The US military said the refineries generated as much as $2 million (£1.2m) per day in revenue for IS.
US President Barack Obama has vowed to dismantle the IS “network of death”.
IS has seized large areas of Syria and Iraq in recent months and controls several oilfields. Sales of smuggled crude oil have helped finance its offensive in both countries.
The US has launched nearly 200 air strikes against the militants in Iraq since August and expanded the operation against IS to Syria on Monday.
On Wednesday, the UN Security Council adopted a binding resolutioncompelling states to prevent their nationals joining jihadists in Iraq and Syria.
President Obama chaired the session and said nations must prevent the recruitment and financing of foreign fighters.
The US military said the fresh air strikes, using fighter jets and drones, hit “small-scale” refineries that were producing “between 300-500 barrels of refined petroleum per day”.
“We are still assessing the outcome of the attack on the refineries, but have initial indications that the strikes were successful,” the US Central Command said in a statement.
The UK-based Syrian Observatory for Human Rights, an activist group that monitors the Syrian conflict, said the strikes killed 14 IS fighters in Deir al-Zour and five civilians in Hassakeh.
Coalition growing
The US says more than 40 countries have offered to join the anti-IS coalition.
France said its fighter jets were carrying out air strikes in Iraq again on Thursday, a day after the beheading of a French hostage in Algeria by an IS-linked jihadist group.
The French military has been carrying out air strikes in Iraq since last week but has not taken part in anti-IS operations in Syria.
UK Prime Minister David Cameron says the British military is also ready to “play its part” against IS.
The UK Parliament has been recalled to discuss plans for air strikes against IS on Friday.
On Wednesday, the Dutch government said it was deploying six F-16 fighter to join the US-led air campaign.
