Iraqi forces are set to launch an offensive to drive Islamic State out of Anbar province.
The start of the operation - backed by Shi'ite and Sunni forces - was announced on state television, although no further details were given.
IS seized large parts of Anbar in early 2014 and militants recently captured the provincial capital Ramadi.
Iraq's prime minister said yesterday that he was confident his troops would retake Ramadi "in days".
Iraqi forces will retake the city of Ramadi from Islamic State militants "in days", the country's prime minister has said.
Thousands of civilians fled the city, which lies around 78 miles from Baghdad, after insurgents seized control.
"It makes my heart bleed because we lost Ramadi, but I can assure you we can bring it back soon," Haider al-Abadi told the BBC.
He defended the Iraqi military amid criticism from US Defence Secretary Ashton Carter, saying they were overwhelmed by the "onslaught" of IS.
"They have the will to fight but when they are faced with an onslaught by Daesh [IS] from nowhere, with armoured trucks packed with explosives, the effect of them is like a small nuclear bomb - it gives a very, very bad effect on our forces."
An eyewitness and a local official have said a convoy of Shi'ite militia fighters and Iraqi army forces set out from a base near the western provincial capital of Ramadi, heading towards areas controlled by Islamic State militants.
Anbar provincial council member Azzal Obaid said hundreds of fighters, who arrived at the Habbaniya air base last week after Ramadi was overrun by Islamic State, were in Khalidiya and were approaching Siddiqiya and Madiq, towns in contested areas near Ramadi.
While pro-government forces are seeking to retake Ramadi, Islamic State insurgents have been pushing forward in the direction of Fallujah in a bid to take more territory in Anbar province that would bring them closer to the Iraqi capital Baghdad.
A British suicide bomber who helped Islamic State militants advance into Ramadi was a popular body-building schoolboy, ITV News can reveal.Read the full story ›
A judge has paid tribute to a 'deeply compassionate' American soldier killed by a landmine planted by British bombmaker Anis Sardar.
Sardar, 38, of Llanover Road, Wembley, London, was sentenced to life in prison with a minimum of 35 years in court today after being found guilty of murder and conspiracy to murder.
One of the IEDs he helped build exploded beneath a US armoured vehicle, killing Sgt First Class Randy Johnson, of 2nd Stryker Cavalry Regiment, who was posthumously awarded the Purple Heart and Bronze Star medals.
Sitting at Woolwich Crown Court, Judge Mr Justice Globe told Sardar that commanding officer Major Eric Adams had described Sgt Johnson as showing "deep compassion" in leading his platoon.
It is therefore the saddest irony that when the eight-wheel Stryker vehicle containing the American soldiers ran over and exploded an IED it was Sgt First Class Johnson who was killed.
He was buried in Arlington Cemetery and his family can be proud that he was awarded the Purple Heart and Bronze Star.
Sgt First Class Johnson's loss was one of the sad tragedies in what was going on in Iraq in 2007.
By the jury's verdict it is a loss for which you are directly responsible.
A British bombmaker who fashioned "professionally-made" IEDs which amounted to landmines in Iraq had viewed American soldiers as the "the enemy", a judge has said.
Sitting at London's Woolwich Crown Court, Mr Justice Globe rejected Anis Sardar's claim that he had only been involved once in making bombs to try to protect the Sunni Muslim community from Shia militants.
I am satisfied so as to be sure that your actions were not solely focused on Shia militias. Your focus was either wholly or party American.
I am satisfied that at the material time of the offences you had a mindset that made Americans every bit the enemy as Shia militias. Both were in your contemplation at all times.
One of the bombs killed American soldier Sgt Randy Johnson.
Sardar, of Wembley, London, was sentenced to life with a minimum of 38 years for murder, and life with a minimum 25 years for conspiracy to murder, to run concurrently.
A British bombmaker who helped build an IED which killed a US soldier in Iraq has been sentenced to life in prison with a minimum of 38 years.
Anis Abid Sardar, 38, of Llanover Road, Wembley, London , was found guilty of murder and conspiracy to murder at London's Woolwich Crown Court yesterday.
The court heard he, along with an accomplice, built a number of explosives as party of a deadly campaign to kill American troops fighting in the county in 2007.
One of the bombs exploded directly beneath an armoured vehicle, killing 34-year-old Sergeant First Class Randy Johnson, of 2nd Stryker Cavalry Regiment.
Sardar was finally caught seven years later, after a delicate forensic examination by the FBI's Terrorist Explosive Device Analytical Centre discovered his fingerprints on some of the bombs.
His partner has not been found.
A London taxi driver is due to be sentenced today after becoming the first person convicted in a British court for murder during the Iraq War following a "landmark prosecution".
"Highly dangerous" Anis Abid Sardar, 38, built improvised explosive devices (IEDs) as part of a "deadly" campaign to kill Americans fighting in the country in 2007.
In what is believed to be a legal first, he was convicted yesterday at London's Woolwich Crown Court of murder and conspiracy to commit murder.
One of the IEDs caused the death of 34-year-old Sergeant First Class Randy Johnson, of 2nd Stryker Cavalry Regiment, when it hit the armoured vehicle he was travelling in on September 27, 2007.
A London taxi driver has become the first person to be convicted, in a British court, of murder during the Iraq War.
The fingerprints of bomb maker Anis Sardar were found on roadside devices - intended to blow up American soldiers. One US Army sergeant was killed by such a device in 2007.
From Sardar's home in Wembley, ITV News Correspondent Juliet Bremner reports.