A US hunt for militants linked to al-Qaeda near Iraq's border with Syria has gone into its second day, with marines leading the way on the ground.
Recent US offensives have focused on Iraq's border with Syria
The US military says it killed eight "armed terrorists" on the first day of Operation Iron Fist which began near the town of Sadah, in Anbar province.
Hospital officials in the town of Qaim said 11 people were killed in US air attacks, including an ambulance driver.
About 1,000 US troops are taking part in the ongoing military operation.
Combat helicopters are also being deployed in the Euphrates Valley for the operation.
The US military statement said the aim was to deny militants the "ability to operate freely... and to prevent the terrorists from influencing the local population through murder and intimidation".
But most residents and insurgents appear to have already fled , the BBC's Richard Galpin reports from Baghdad.
Loud explosions could be heard in the area before dawn on Sunday, continuing for several hours, a hospital official told the BBC.
Iron Fist is the first major assault in western Iraq since US and Iraqi troops struck the town of Talafar - also near the Syrian border - in September.
SEPTEMBER BOMBINGS IN IRAQ
30 Sept: Hilla, 10 killed
29 Sept: Balad, 95 killed
28 Sept: Talafar, 9 killed
17 Sept: Baghdad, 30 killed
16 Sept: Tuz Khurmatu 10 dead
15 Sept: Baghdad, 29 dead
14 Sept: Baghdad, 112 dead
No Iraqi troops are being used in the current operation, our correspondent notes.
The US offensives have largely failed to stop a series of deadly bombings blamed on the insurgents.
Violence has spiralled as Iraqis prepare to vote in a referendum on a new constitution, scheduled for 15 October.
Last week, bombs in the town of Balad claimed 95 lives and 10 in Hilla.
In Baghdad, gunmen have shot dead a top official in the ministry of public works.
Police said the official, Safaa Muhammed, the director-general of the ministry, was killed in the Mansour district of western Baghdad.
Meanwhile, the US has freed 500 detainees from Abu Ghraib prison, near Baghdad, bringing the total number of prisoners released in the last few days to 1,000.
The US said the freed prisoners were not guilty of serious crimes.
Their release has been timed with the Muslim holy month of Ramadan, due to start this week.
Abu Ghraib prison became synonymous with the mistreatment of detainees after pictures emerged last year of US soldiers abusing Iraqi captives.