The US-led coalition has carried out air strikes on the Iraqi city of Ramadi, which fell to the Islamic State of Iraq and the Levant (ISIL) group this week, according to US administration sources.
The assault comes a day after the UN said that at least 25,000 people had fled the city in advance of an expected battle.
"We have done air strikes today in Ramadi, I have been told," a US State Department official said on Wednesday.
"When we see targets, we are going to take them out."
Iraqi forces, for their part, said they fought off an overnight attack by ISIL near Ramadi, whose loss was the most significant setback for the government in a year.
Government forces backed by Shia units have been assembling at a base near Ramadi in preparation for a counterattack to retake the city.
The Habbaniya base is midway between Ramadi and the town of Fallujah, which has been under ISIL control for more than a year and is 50km from the Iraqi capital, Baghdad.
|Many civilians fleeing Ramadi spend their days on the road waiting for permission to enter Baghdad [Zeina Khodr/Al Jazeera]
ISIL fighters have taken tanks, artillery and large amounts of ammunition abandoned by fleeing Iraqi forces.
"Daesh attacked us around midnight after a wave of mortar shelling on our positions," Amir al-Fahdawi, a leader of the pro-government Sunni tribal force in the area, told Reuters news agency on Wednesday, using the Arabic word for ISIL.
"This time they came from another direction in an attempt to launch a surprise attack, but we were vigilant and, after around four hours of fighting, we aborted their offensive."
Sabah Karhout, head of the Anbar provincial council, said: "They want to occupy more of Anbar. Their primary aim is to connect Ramadi to Fallujah."
The UN said on Tuesday that it is rushing to aid nearly 25,000 people fleeing Ramadi for the second time in a month after ISIL seized the city.
Meeting in Paris
Against this backdrop of escalating conflict, France has announced it will host a high-level meeting on the crises in Iraq and Syria on June 2.
Laurent Fabius, the French foreign minister, announced at a cabinet meeting on Wednesday that "there would be a meeting in Paris on the whole situation in Syria and Iraq".
He said John Kerry, the US secretary of state, would be among the attendees.
Along with representatives from top international organisations, up to 24 ministers - including Frank-Walter Steinmeier, the German foreign minister - will travel to the French capital, diplomatic sources said.
The announcement of the meeting came as ISIL fighters reportedly overran the whole of the historic Syrian city of Palmyra.
|Iraqis have been fleeing Anbar for safe areas in large numbers as Shia units prepare to recapture Ramadi [Zeina Khodr/Al Jazeera]
In another development on Wednesday, Haider al-Abadi, Iraq's prime minister, flew to Russia seeking closer military cooperation with his country.
Abadi, who is due to meet President Vladimir Putin on Thursday, heads a large delegation that includes several ministers and a number of civil and military advisers.
The focus will be "the development of relations between the two countries, mainly expanding the military and security cooperation, and support for Iraqi forces in the face of terrorism", Abadi's office said.
Amid delays in the delivery of some US weaponry that Iraq has been expecting under an agreement with the US, Iraq is said to be increasingly looking to Russia, China and Iran for military purchases.