Centcom did not call Thursday night's explosion a suicide bombing but the circumstances were similar to those of a car bomb blast on March 29, which Iraq said would be followed by others against US and British troops.

Coalition forces were controlling a checkpoint 18 kilometers (seven miles) from Hadithah Dam in Iraq when a vehicle drove up and a pregnant woman stepped out "screaming in fear," a Centcom statement said.

As soldiers approached, the vehicle exploded. The woman and the car's driver were killed along with three coalition troops. Two other soldiers were injured, Centcom said.

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