U.S. and Iraqi forces have launched the second operation targeting insurgents in western Anbar province in the past two days.
About 1,000 troops began Operation Dagger Saturday in a remote lake region northwest of Baghdad.
U.S. military officials say the operation is aimed at finding hidden weapon stashes and insurgent camps.
This the same area where U.S. and Iraqi forces killed a large number of insurgents in March.
Earlier, military officials said about 50 insurgents have been killed 100 captured near the town of Karabilah in a separate operation launched Friday.
Troops found four Iraqi hostages beaten and chained to a wall in a bunker.
Some information for this report provided by AP and Reuters.