Al-Zarqawi's Tawhid and Jihad group has claimed responsibility for beheading several foreign hostages and for car bombings throughout the country, and a videotape posted Wednesday on an Islamic Web site showed militants linked to al-Zarqawi beheading two Iraqis they accused of being intelligence officers.
The beheadings came as U.S. forces put pressure on insurgent strongholds in the Sunni heartland.
The Islamic holy month of Ramadan begins Friday, and some extremists believe they earn a special place in paradise if they die in a jihad, or holy war, during Ramadan, when Muslims believe God revealed their holy book the Quran to the Prophet Muhammad.
Iraq's deteriorating security of bombings, mortar and rocket attacks, kidnappings and shootings slows reconstruction efforts and forces the United States to divert funds from rebuilding to security.
Wednesday, a driver plowed into a U.S. convoy and blew up his car in the northern city of Mosul, killing two American soldiers and wounding five, according to the military. Four other soldiers were killed in roadside bombings in the Baghdad area - three late Tuesday and one early Wednesday, U.S. command said.
Last year, the advent of Ramadan was marked by a surge in attacks. To prevent a repeat, U.S. troops have stepped up offensive operations in Sunni Muslim strongholds to the north and west of Baghdad.
More than 1,000 U.S. and Iraqi troops launched two simultaneous raids Wednesday around Baqouba, 35 miles northeast of Baghdad, to clear the area of insurgents.
''Basically, it's a pre-Ramadan operation just to clear up some of the area around Baqouba,'' said Capt. Marshall Jackson, spokesman for the 3rd Brigade, 1st Infantry Division.
There were no reports of major clashes, but several people were detained. In an unrelated attack, a police captain was killed Wednesday in a drive-by shooting near Baqouba, officials said. Insurgents regularly target Iraq's security forces, who are seen as collaborators with the United States and its allies.
Elsewhere, U.S. troops sealed off key streets and searched buildings in the insurgent stronghold of Ramadi after days of clashes, residents reported.
