A homicide car bomber killed at least three Iraqis Monday near the Green Zone housing the U.S. Embassy and Iraqi government, and the U.S. military said three American servicemen died in roadside bombings.

The U.S. military also said it was preparing to bolster its forces in training Iraqi police.

U.S. and Iraqi authorities conducted joint operations in an intensive effort to free kidnapped American journalist Jill Carroll, who was abducted Jan. 7 in Baghdad. Carroll's father pleaded for her life in a televised interview on Sunday night.

The bomber targeted a police patrol near the Iranian Embassy, which is close to the checkpoint into the Green Zone known as the "Assassins' Gate," said the top Baghdad police officer, Maj. Gen. Abdul-Razaq al-Samarie.

Two civilians and a policeman were killed and six Iraqis were wounded, including five policemen, al-Samarie said.

A roadside bomb killed a U.S. soldier Monday during a patrol in southwestern Baghdad, the military said in a statement. The soldier was attached to the Multi-National Division-Baghdad.

Two U.S. airmen were killed and a third was wounded in an attack on a convoy Sunday near Taji, where a U.S. air base is located 12 miles north of Baghdad, the military said.

The deaths brought the number of U.S. military personnel killed since the war in Iraq began in March 2003 to at least 2,227, according to an Associated Press count.

Another car bomb exploded on a highway about 20 miles south of Baghdad, killing one Iraqi civilian and wounding four others, said police Capt. Hussein Shamil. Drive-by gunmen also shot dead a doctor who worked at the Iraqi Health Ministry as he drove to work in Baghdad's Saydiyah neighborhood, said police Capt. Qassim Hussein.

Armed men, some wearing police commando uniforms, raided homes and a mosque in a predominantly Sunni Arab neighborhood of northern Baghdad on Monday. They shot and killed three men on the spot and detained more than 20, police said.

Dozens of gunmen poured out of seven cars and barged into houses and a mosque, dragging males out of their beds and driving them away, said Maj. Falah al-Mohammedawi.

The killings and detentions threatened to worsen sectarian tensions in the capital, where Sunni Arabs accuse Shiite militiamen and security forces of assassinating and kidnapping Sunnis.

Hundreds of enraged, wailing Sunnis took to the streets in the neighborhood of Toubji, calling for revenge and firing guns into the air as groups of men carried coffins carrying those slain to a nearby cemetery.

The violence comes as Iraqi politicians try to form a national unity government including members of Iraq's main Shiite, Kurdish and Sunni Arab political parties. The bulk of Iraq's insurgency has been linked to Iraq's Sunni Arab community, and involving it in the next government is seen as a way to reduce the violence.

Carroll's father pleaded with his daughter's captors to release the 28-year-old freelance journalist.

"She is not your enemy," Jim Carroll said in a televised interview.

"Jill started to tell your story, so please, let her finish it," he said in a statement. "Through the media, if necessary, advise her family and me of how we might initiate a dialogue that will lead to her release."

He said his daughter is "honest, sincere and of good heart" and has great respect for the Iraqi people. "When you release her alive, she will tell your story with that same conviction," he added.

Carroll has not been heard of since her kidnappers released a videotape that was first aired on Jan. 17. It was accompanied by a threat that she would be killed if U.S. forces did not release all Iraqi women in military custody.

Iraqi Deputy Justice Minister Busho Ibrahim Ali said six of the nine women were expected to be freed later this week as part of a routine release planned before the kidnappers' ultimatum. But he believed the U.S. military was wary about the releases being seen as part of a swap for Carroll.

A U.S. official, speaking on condition of anonymity due to the sensitivity of the efforts to free Carroll, said American authorities refuse to negotiate with hostage-takers.

"But we are using the full resources available from the U.S. law enforcement and diplomatic side, plus the cooperation of the Iraqi government, to secure Jill's freedom," the official said.

Jim Carroll said he was "very encouraged" by the support for his daughter and his family's plight.

"We're getting by," he said. "It is very difficult, as you might imagine. But, again, the amount of support from family, friends, and total strangers around the world sending us messages of support and all of their prayers has been very encouraging."

Another hostage, Jordanian Embassy driver Mahmoud Suleiman Saidat, appeared in footage aired on Al-Arabiya TV pleading for his life. His captors also extended the deadline to kill Saidat, who was kidnapped on Dec. 20.

The kidnappers said they were giving neighboring Jordan more time to cut ties with the Iraqi government. They also want Jordan to free a female would-be bomber whose explosives belt failed to go off during Nov. 9 attacks that killed 60 people at three hotels in the Jordanian capital, Amman. Al Qaeda in Iraq has claimed responsibility.

More than 250 foreigners have been taken hostage in Iraq, either by insurgents or gangs, since the 2003 U.S.-led invasion that toppled Saddam. At least 39 have been killed.

In efforts to stem the continuing violence across Iraq, the U.S. military said more than 3,000 Americans will staff new Police Training Teams in Iraq, dubbing 2006 "the year of the police." They will include military police, soldiers, translators, communications and logistics specialists, the Associated Press Radio has learned.

Their deputy commander, Col. Donald Currier, said that in the past, the United States focused on recruiting officers. He said not enough attention was paid to getting the systems in place to equip and pay the officers on the beat.

The training emphasis in the Iraqi provincial offices will be on such areas as payroll and logistics, but Currier said the focus in police stations will be on hands-on skills, including community relations.