Updated

BAGHDAD-- Twin car bombings in the northern Iraq, and separate attacks on the homes of a schoolteacher and a human rights activist left at least 11 people dead on Saturday, government officials said.

Violence is raking Iraq as the Shiite-led government and other political factions are debating a request for some American forces to remain in the country beyond the Dec. 31 deadline for all U.S. troops to withdraw after more than eight years.

While violence is well below what it had been during intense Shiite-Sunni sectarian fighting in 2006 and 2007, militants are again stepping up deadly attacks. That has led to concerns about what happens when the 47,000 remaining U.S. troops are withdrawn.

Police and hospital officials in the northern city of Mosul said two car bombs exploded in quick succession, killing six people. At least one of the bombs seemed aimed at a police patrol. Mosul is Iraq's third largest city, 225 miles northwest of Baghdad. It has been one of the most stubborn insurgent strongholds.

Abdul-Rahim al-Shimmari, a member of the provincial council, said 52 people were wounded in the blast.

The force of the explosion shattered the windows and mirrors in a nearby barber shop, and caused the false ceiling to collapse.

"Fortunately, none of us were wounded, but one of my customers, whose hair was half cut, ran away out of fear," said the owner, Mahir al-Abbawi.

Security forces opened fire randomly in all directions after the first explosion, he said.

"After about four minutes, we saw a ball of fire coming out of another car that was about 10 meters away from the first explosion," he added. Al-Abbawi said he could see people bleeding and women and children screaming and crying.

In another attack, eight gunmen stormed the house of a schoolteacher overnight and killed his three sons and daughter, said Mohammed al-Asi, the spokesman for central Salahuddin province.

He said the gunmen were in a minibus and fled after the midnight attack in a village outside of Tikrit. Authorities were investigating whether the killings were an act of insurgents or tribal conflict, he added.

Tikrit is Saddam Hussein's hometown and is located 80 miles north of Baghdad.

Authorities in a suburb in western Baghdad, police in Abu Ghraib found the body of a human rights activist, Namir Ryhan, inside his home, a police and hospital official said. Both officials said assailants beheaded the activist.

There was no immediate claim of responsibility; Sunni militants, including Al Qaeda, have been known to behead their victims.