Police said they suspected the gunmen were Sunnis seeking to intimidate Shiites into fleeing the area south of Baghdad. Previous major attacks in Iraq have killed many women and men together, and at times individual women have been shot or kidnapped. But rarely have large groups of women been attacked.

In another sign of sectarian bloodshed, police in Duluiyah north of Baghdad found 14 beheaded bodies thought to be from a group of 17 workers kidnapped by gunmen Thursday while traveling home to the mostly Shiite town of Balad. There was no word on the other abductees.

The attack on the farm field took place outside Saifiya, an ethnically mixed village south of Baghdad. Most residents already fled to escape violence, Sunnis going to the nearby town of Madain, Shiites to neighboring Suwayrah.

The women were gathering vegetables when gunmen pulled up in two cars around 8 a.m. and surrounded the field. They opened fire, killing six women and two girls about 4 or 5 years old, Lt. Mohammed al-Shammari said. The attackers forced two teenage girls into the cars and escaped, he said.

Al-Shammari said the gunmen may have come from the nearby Baghdad district of Dora, a mixed neighborhood long torn by bloodshed inflicted by both Sunni insurgents and Shiite militiamen.

Baghdad has been the epicenter of violence for months. The city has averaged 36 attacks a day the past three weeks, an increase of nearly 30 percent over the preceding seven weeks and 60 percent higher than from mid-March to mid-June, according to U.S. military figures.

The U.S. military spokesman, Maj. Gen. William Caldwell, attributed the rise to the Islamic holy month of Ramadan, when he said attacks "historically" have increased. Some Islamic militants believe that dying in combat during Ramadan brings extra blessings in paradise.

U.S. officials warned weeks ago that killings by Shiite and Sunni death squads have become the greatest threat in Iraq, although the Sunni-dominated insurgency continues bombing and shooting attacks on U.S. and Iraqi troops as well as civilians.

Besides the attack on the women, at least 10 other Iraqi civilians died in violence Friday. A U.S. soldier was killed by a roadside bomb in northern Iraq, the 45th American death this month.

Bloodshed in Baghdad itself was tamped down by a curfew ¡ª imposed every Friday, banning vehicle traffic to prevent car bomb attacks on weekly Muslim prayers.

The northern city of Mosul was also under curfew after U.S. and Iraqi troops fought with gunmen Thursday night. The fight was sparked by a mortar barrage on a U.S. base that wounded 12 American soldiers. At least 12 suspected insurgents were reported killed in ensuing gunbattles.

The head of Iraq's most feared Shiite militia, the Mahdi Army, issued a statement late Thursday disavowing violence committed against Iraqis in the name of his group. But it was unclear whether he referred to slayings of Sunnis or minor clashes with other Shiite militias.

In pamphlets distributed in his hometown of Najaf, 100 miles south of Baghdad, radical Shiite cleric Muqtada al-Sadr ¡ª whose party is also a powerful member of the government ¡ª said members of his militia had not been involved in any "unlawful attacks" on Iraqis.

"This has not been proven, but if it is shown to be true I will publicize their names and disavow them," al-Sadr said.

"They should make use of the holy month of Ramadan and repent," he added.

Meanwhile, a new video on the Internet hinted at possible splits between Iraqi Sunni insurgents and al-Qaida in Iraq, the group behind many of the country's worst bombings and whose fighters are thought to be mostly foreign Arabs.

A man claiming to be an Iraqi Sunni insurgent appears on the video urging Osama bin Laden to replace the leader of al-Qaida in Iraq because of its attacks on Sunni clerics.

"They planted explosives in the houses, the hospitals and the schools and even the electric transformers," the man, who called himself Abu Osama al-Iraq, said in the video.

He warned that if insurgents lose Sunni support, "we will be an easy hunt for the crusaders, the occupiers and their agents the Shiites." He asked bin Laden to name an Iraqi to replace Abu Ayyub al-Masri as leader of al-Qaida in Iraq.

Al-Masri ¡ª whose pseudonym means "the Egyptian" ¡ª took over the leadership after Abu Musab al-Zarqawi was killed by a U.S. airstrike in June. Other Sunni insurgents had criticized al-Zarqawi, a Jordanian, for turning Sunni Iraqis against the movement by killing civilians.

The authenticity of the video, posted on a Web forum often used by Islamic militants, could not be confirmed. But it was the first report of dissent toward al-Masri.