Eight members of one Shiite family were killed south of Baghdad in the worst incident of a bloody day across Iraq that left at least 23 dead. The spate of attacks — and the fact that some of the family were beheaded — raises fears that insurgents are trying to re-ignite sectarian warfare at a time when the country is preparing for critical March elections.

The March 7 election will determine who will oversee the country as the U.S. forces go home, and whether Iraq will be able to overcome the deep sectarian divides that almost destroyed it during the height of the fighting in past years.

A "terrorist group" using guns fixed with silencers shot and beheaded eight members of a single family in the village of Wahda, a mixed Shiite-Sunni village 20 miles south of the capital, the Baghdad security command said in a statement.

Authorities provided no further details about how many were shot, how many beheaded and provided little other information about what they described as an "ugly crime." But beheadings have been performed before by extremist Sunni insurgents.

Associated Press television video of the attack showed a blood-soaked mattress and carpet, and stuffed animals strewn across the floor.

AP video from the nearby police station showed four people who authorities said were responsible, but no further details were given. The police statement did not indicate who might have carried out the attack.

"The crime of killing my brother, his wife and six children, five girls and one boy, is an ugly and ruthless crime," said Mahdi Majid Maryoush al-Qabi, a brother to the killed father of six. "I call upon the Iraqi government and the prime minister to execute the accused immediately at the crime scene so that they will set an example for others. They are devoid of any human values."

A Baghdad police officer and witnesses said the family belonged to Iraq's Shiite Muslim majority. The police officer said the family had been displaced from their home during the sectarian fighting in 2006 and had just returned in 2009.

During the fighting of 2006 and 2007, hundreds of thousands of families fled their homes across Iraq due to death threats, killings and kidnappings, as neighborhoods and towns that were once mixed with Sunnis and Shiites were almost emptied of one sect or the other.

As the situation in the country has become safer, Prime Minister Nouri al-Maliki's government has tried to encourage people to return to their previous homes, even offering cash payments to people who return. While the effort has met with some success in certain areas, such a brutal killing could serve as a stark warning to others looking to return home.

The mixed sectarian region south of Baghdad where the deaths occurred was a flashpoint for violence.

All the officials spoke on condition of anonymity due to the sensitivity of the incident.

U.S. military spokesman Brig. Gen. Stephen Lanza said U.S. officials had been worried about a rise in violence ahead of the election, but said it was too soon to tell whether the death of the family of eight, as well as an early morning mortar attack against the Green Zone in Baghdad, were specifically tied to the vote.

"There's still an investigation ongoing into the tragedy that happened in the south against that family, and I don't know if it's a tribal dispute or if it's a dispute for other issues in terms of any kind of crime or something to that effect," he said.

The incident comes as U.S. forces are slated to draw down after the election, but Gen. Ray Odierno, the top U.S. general in Iraq said he could slow troops' exit if Iraq's politics are chaotic following the vote.

Odierno said there are no signs that would be necessary but said he has briefed his superiors about the plan during his meetings in Washington this week.

Six people were hurt after three mortar rounds struck the Green Zone, the neighborhood housing the main Iraqi government compound and the U.S. Embassy, early Monday morning.

In other violence, five people died after a booby-trapped car blew up in Ramadi, the capital of Anbar province, 70 miles (115 kilometers) west of Baghdad, two police officials said.

In Baghdad, gunmen broke into the home of a family, killing all four, police said. However, authorities said the motive might have been robbery, noting that the gunmen took the family's car.

Elsewhere in the capital, a sniper killed a policeman while gunmen killed a street cleaner, authorities said.

In two separate incidents in northern Iraq, gunmen killed a policeman in Kirkuk and two soldiers in the northern city of Mosul, authorities said. In the central city of Tikrit, a sticky bomb attached to a car killed the driver, said a police official.

The officials spoke on condition of anonymity because they were authorized to speak to the media.