Attackers killed nine people in an outburst of violence, including four Christian women headed to jobs at a U.S. military base and two American soldiers. South of the capital, the security chief of Spanish troops in Iraq (search) was shot in the head during a raid.

Two Iraqi policemen were killed Thursday and three others were wounded when gunmen fired on a police checkpoint between Fallujah (search) and Ramadi, two insurgency hotspots west of Baghdad.

The attack occurred along the same road where the day before, assailants firing from a speeding car killed four Christian women and wounded six other people in a convoy headed for the U.S. military base at Habaniyah (search), 50 miles west of the capital.

Askhik Varojan, who worked in the laundry at the U.S. base, had boarded a minibus Wednesday determined to hand in her resignation rather than live in fear from the insurgents targeting those helping the coalition forces.

"She went yesterday to tell them that she wouldn't go to work any more and to claim her salary," Varojan's sister, Eida Varojan, sobbed. She had taken the job at Habaniyah three weeks ago to support her paralyzed husband and four children.

On Thursday, her coffin was brought to the dingy one-room apartment, where relatives gathered to mourn. Her 20-year-old daughter, Anjel, fainted from grief.

"I won't continue this work. I am afraid. They wanted to kill us all," said Vera Ibrahim, 39, who survived when the masked gunmen raked their vehicle with automatic fire.

Elsewhere, two U.S. soldiers were killed and another wounded during a rocket and mortar barrage late Wednesday on an American camp near Baqouba, 35 miles northeast of Baghdad. American troops returned fire, damaging a house, witnesses said.

The deaths of the soldiers brought to 505 the number of American service members who have died since a U.S.-led coalition launched the Iraq war March 20. Most of the deaths have occurred since President Bush declared an end to active combat May 1.

In Madrid, the Spanish Defense Ministry said the security chief for Spanish troops in Iraq was shot and seriously wounded Thursday during a raid against suspected insurgents south of Diwaniyah, headquarters of the 1,300-member Spanish military force in Iraq.

Civil guard commander Gonzalo Perez Garcia was rushed to a U.S. military hospital in Baghdad, where he was in critical condition.

Ten Spaniards have died in Iraq since August, including seven intelligence agents killed in an ambush in November.

In Basra, Iraq's second-largest city, the 23-year-old son of a former senior official from Saddam Hussein's Baath party was slain Thursday by an unidentified attacker. The city is a stronghold of Shiite Muslims who were oppressed by Saddam's Sunni-dominated regime.

The attacks in the Fallujah area followed a period of relative calm there since the arrest Jan. 11 of Khamis Sirhan al-Muhammad, a former Baath party official described as the key leader of the resistance in Anbar province.

It appeared the women were targeted as part of a campaign to discourage Iraqis from cooperating with the occupation forces. On Sunday in Baghdad, a bomb exploded at a gate to coalition headquarters used by Iraqi workers, killing 31 people and wounding about 120 -- most of them Iraqis.

"The message is clear. The [anti-U.S.] elements ... want to turn the clock back on Iraq," coalition spokesman Dan Senor said. "They want to turn back to the era of mass graves and chemical attacks and torture chambers and rape rooms, and they will target Iraqis and Iraqi leaders who want to change that course and move Iraq forward."

Despite the violence, a senior American commander said U.S. forces have brought insurgents "to their knees" since Saddam's arrest Dec. 13 near Tikrit. Maj. Gen. Raymond Odierno, commander of the 4th Infantry Division based in Tikrit, said Saddam's arrest "was a major operational and psychological defeat for the enemy."

Odierno, whose troops are preparing to leave Iraq in several weeks, said that although former Baath loyalists are no longer a major threat, the nature of the anti-American violence could shift, fueled by what he called a nationalistic motive to get U.S. troops to leave.

He defined the threat as being posed by "those that really just want Iraqis to run their own country," and "elements that are going to try to use Iraqi nationalism to say we need to get the Americans and the coalition forces out of Iraq, and they will continue to attack us."

Coalition officials hope such hostility will diminish after the United States and its allies transfer sovereignty to a new Iraqi leadership by July 1. Coalition officials will gradually shift security responsibility to the Iraqis.

However, the U.S. blueprint has been threatened by a dispute with the country's most influential Shiite cleric, Grand Ayatollah Ali al-Husseini al-Sistani. He opposes the U.S. plan to select a new provisional legislature through 18 regional caucuses, demanding direct elections instead.

U.S. officials insist early elections are impossible due to the security situation, lack of voter rolls and the absence of an election law.

U.S. administrator L. Paul Bremer has asked the United Nations to send experts to Iraq to determine if early elections can be held. Al-Sistani's allies have said the ayatollah would accept the U.N. findings.

On Thursday, an aide to al-Sistani said the cleric wants Iraqi experts to concur with the U.N. findings before he would accept them. Mohammed al-Yehia al-Mawsawi, a spokesman for al-Sistani, said the ayatollah wanted to hear "alternatives" for choosing a new assembly if U.N. experts recommend against elections.