Three Iraqi policemen were killed Monday in an ambush on their checkpoint northeast of Baghdad, police said. One other officer and two civilians were wounded in the attack, which took place at dawn in the Zaghinya area near Baqouba, the troubled capital of Diyala province. Baqouba lies 60 kilometers northeast of the Iraqi capital. Meanwhile, a car bomb exploded in front of a police officer's house farther north, wounding ten people - mostly women and children, police said. 1st Lt. Miyasser Hassan was not home when the bomb went off around 7:15 a.m. near his doorstep in Albu-Jawari village, on the northern outskirts of Beiji, about 250 kilometers north of Baghdad.