BAGHDAD, Iraq — Iraqi Prime Minister Nouri al-Maliki upbraided the U.S. military over allegations that Marines killed two dozen unarmed civilians in Haditha, calling the killings "a horrible crime" in his strongest public comments on the subject.

The U.S. military ordered coalition troops in Iraq on Thursday to undergo special training in ethics and "the values that separate us from our enemies" in the wake of the Haditha allegations.

The order came as Iraq's government began its own investigation of the deaths last November in the western town as well as other incidents involving U.S. troops.

Al-Maliki said the list of human rights breaches by coalition forces is long.

"This is a phenomenon that has become common among many of the multinational forces," the prime minister said. "No respect for citizens, smashing civilian cars and killing on a suspicion or a hunch. It's unacceptable."

Al-Maliki's remarks bolstered Iraqi complaints that U.S. troops are insensitive to their culture and show disregard for their lives.

The Americans, on the other hand, are under intense pressure, isolated from Iraqis by cultural and language barriers and battling insurgents who easily blend into the civilian population.

The U.S. military is conducting at least two investigations into the killings of civilians, including women and children, in Haditha on Nov. 19.

The killings followed the death that day of a Marine in a bomb explosion that targeted a military convoy. Rep. John Murtha, D-Pa., a decorated war veteran who has been briefed by military officials, has said the Marines, angered by the loss of a comrade, shot and killed civilians in a taxi near the scene and went into nearby homes and shot others.