U.S. forces have arrested a father and son suspected of carrying out an attack on a forward base that killed two American soldiers, a military spokeswoman said Friday.

The soldiers were among nine people, including four Christian women headed to jobs at a U.S. military base, killed in a spate of attacks on Wednesday and Thursday. South of the capital, the security chief of Spanish troops in Iraq was shot in the head during a raid.

The two suspects were detained Thursday without incident at their home in Hadid (search), a village close to Baqouba (search), 35 miles northeast of Baghdad, said Maj. Josslyn Aberle, spokeswoman for the 4th Infantry Division (search). No other details were available.

The U.S. base, near Baqouba, was hit by a barrage of rockets and mortars on Wednesday night, killing the two soldiers and wounding another. The deaths raised to 505 the number of U.S. service members who have died since the U.S.-led coalition launched the Iraq war on March 20.

Baqouba is about 80 miles southeast of Tikrit. The two cities are part of the so-called Sunni Triangle, where most of the insurgent attacks against U.S.-led coalition troops have taken place since the invasion.

Two Iraqi policemen were killed Thursday and three others were wounded when gunmen fired on a police checkpoint between Fallujah and Ramadi, two other 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, 50 miles west of the capital.

Relatives said 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. Askhik 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.

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.

"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."

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.