U.S-led anti-insurgent operations are continuing in western Iraq, in an effort to prevent attacks on voters in the lead-up to next week's constitutional referendum. The U.S. military reports on Friday says that six Marines were killed Thursday in two roadside bomb explosions in the area of operations along the Euphrates River. Officials also report air strikes Wednesday on a building used by al-Qaida terrorists in the same area killed 20 suspected terrorists. Nine other insurgents were killed in two other incidents. Meanwhile, in the southern city of Basra, British officials say they have detained 12 people, including members of the local police force. They are suspected of involvement in a surge of attacks on British forces in the area.