The US-led coalition against the self-styled Islamic State has conducted 19 air strikes in the vicinity of the Iraqi city of Ramadi over the past 72 hours.
The strikes targeted IS fighting positions,armoured and technical vehicles, and buildings they control.
Shia paramilitaries are also preparing to deploy to Iraq's western province of Anbar after IS militants overran Ramadi.
A spokesman for the paramilitaries, known as Hashid Shaabi, said they had received orders to mobilise, but details could not be revealed for security reasons.
Iraqi Prime Minister Haider al-Abadi signed off on the deployment to attempt to seize back the predominately Sunni area, a move he had previously resisted for fear of provoking a sectarian backlash.
The fall of Ramadi marks a major setback for the forces ranged against Islamic State.
It is also a harsh return to reality for the US, which at the weekend mounted a successful special forces raid in Syria in which it said it killed an IS leader in charge of the group's black market oil and gas sales, and captured his wife.
While the Iraqi government and Shia paramilitaries recaptured the city of Tikrit from IS last month, the major northern city of Mosul remains under the control of the Islamists.
IS said it had seized tanks and killed "dozens of apostates", its description for members of the Iraqi security forces, in Ramadi.
Earlier, security sources said government forces evacuated a military base after it came under attack by the insurgents, who had already taken one of the last districts still holding out.
It was the biggest victory for Islamic State in Iraq since security forces and Shia paramilitary groups began pushing the militants back last year, aided by air strikes from a US-led coalition.
US Secretary of State John Kerry has expressed confidence the takeover of Ramadi would be reversed in the coming weeks.
Mr Kerry told a news conference in Seoul, South Korea that Ramadi had been a target of opportunity for the Islamist militants.
The US Defense Department has also tried to play down the impact of the seizure on the broader Iraq military campaign.
The Iraqi government had vowed to liberate Anbar after defeating the militants in Tikrit.
However, the security forces, which partly disintegrated under an Islamic State onslaught last June, have struggled to make progress in the vast desert province.
