Iraqi forces are reported to have launched an operation to recapture the last stronghold of so-called Islamic State in the country's western desert.
A military source told the BBC that soldiers, Anbar provincial police and Sunni Arab tribal fighters began moving on the town of Ana on Tuesday morning.
Their progress was slowed initially by dozens of booby-traps, the source said.
Ana, 90km (55 miles) from the Syrian border, is one of three Iraqi towns in the Euphrates river valley held by IS.
The jihadist group still controls large parts of the valley in the neighbouring Syrian province of Deir al-Zour, but it is under pressure there from Syrian pro-government forces and a US-backed alliance of Kurdish and Arab fighters.
The Iraqi military source said the assault on Ana and its surrounding district was being supported by US-led coalition air strikes and military advisers on the ground.
Coalition warplanes had destroyed an explosives-packed car driven by a suicide bomber shortly after the start of the operation, the source added.
After retaking Ana, the troops will target Rawa, 12km (7.5 miles) to the north, and then al-Qaim, the last town before the border with Syria.
"The objective is to bring the entire province of Anbar back into the fold of the nation," Lt Gen Rashid Flaih, head of Anbar's paramilitary units, told AFP news agency on Monday.
The launch of the Ana offensive comes as Iraqi forces prepare for an assault on Hawija, another IS stronghold 220km (135 miles) north of the capital Baghdad.
IS has suffered a series of defeats in Iraq in recent months, with the government declaring that the second city of Mosul had been recaptured in July.