BAGHDAD, Iraq (CNN) -- Coalition forces on Thursday arrested a suspected member of an elite Iranian unit that has been accused of training and equipping insurgents in Iraq, the U.S. military said.

An Iraqi soldier guards the scene of a car bomb Thursday in eastern Baghdad.

The military said the suspect, who was not identified, is a member of Iran's Islamic Revolutionary Guard Corps - Quds Force.

The U.S. military calls the force "a covert action arm of the Iranian government responsible for aiding lethal attacks against the Iraqi government and coalition forces."

The military said the Quds Force suspect was involved in bringing roadside bombs from Iran into Iraq and in training foreign terrorists in Iraq.

The man, captured in the Iraqi Kurdish city of Sulaimaniya, is one of several Iranians in U.S. custody in Iraq.

Also on Thursday, an Iraqi National Police intelligence officer was taken into custody for "suspected involvement in illegal militia activities," the U.S. military said.

Col. Thamir Mohammad Sinah al-Husayni, also known as Abu Turab, was arrested by U.S. troops.

The officer used his position "to direct Iraqi National Police officers to use traffic checkpoints throughout western Baghdad to detain Sunnis, thereby aiding in sectarian evictions in Shia areas," the military said.

The military also said he abused Sunni detainees and used them to obtain ransom.

Meanwhile, two Iraqi soldiers were among three people killed Thursday when a parked car detonated near an Iraqi Army checkpoint, an Interior Ministry official said.

The official said a tow-truck driver hauling a car approached the checkpoint and asked troops if he could drop off the vehicle he was towing near the checkpoint because he had to tow another car.

The driver dropped the car off and left. Moments later, the parked car blew up, the Interior Ministry official said

The bomb exploded in the Habibiya neighborhood at the edge of Sadr City, the densely populated Shiite slum in northeastern Baghdad. Seven people were wounded, including four soldiers.

Coalition forces elsewhere in Iraq on Thursday killed seven suspected al Qaeda in Iraq insurgents and detained eight others, the U.S. military said.

The seven were killed in fighting during a raid in Mahmoudiya, southwest of Baghdad. Three people were detained there.

North of Baghdad in Samarra, five people were seized in another raid.

Lt. Gen. Raymond Odierno, a top U.S. commander in Iraq, told reporters Thursday that attacks across the nation have dropped "to their lowest levels" since the strike in February 2006 on the Askariya mosque in Samarra, an attack that spurred intense sectarian violence.

And in Baghdad, he said, civilian casualties have dropped since last year from an average of 32 per day to 12 per day.

The U.S. military announced the non-combat death of an American soldier Wednesday in Iraq's Anbar province.

This brings the number of U.S. troop deaths in the war to 3,785; seven civilian contractors for the Defense Department also have been killed. Fifty U.S. troops have died in Iraq so far in September. E-mail to a friend

CNN's Mohammed Tawfeeq contributed to this report.

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