BAGHDAD – Iraqi police fatally shot a Kurdish politician in one of Iraq's most volatile provinces Saturday, a killing that underlines the growing tensions between Kurds and Arabs in parts of the north.

Even as Iraq has seen a sharp decline in Sunni-Shiite sectarian violence, hostility is deepening between Kurds and Arabs in Iraq's north as Kurdish authorities begin to exert more authority beyond the boundaries of their autonomous region.

Riya Qahtan, a member of the Kurdistan Democratic Party, was killed Saturday morning in Jalula, a small town 80 miles (125 kilometers) northeast of Baghdad in the ethnically mixed province of Diyala, said Jabar Yawer, a spokesman for the Kurdish military, or peshmerga. Jalula has a mostly Sunni Arab population with a substantial Kurdish minority.

The incident occurred after two Sunni Arab policemen stopped three members of the Kurdish secret service at a market and demanded they show identification. They refused, and within minutes police reinforcements arrived at the scene, arrested them and took them to police headquarters, Yawer said.

Qahtan then went to the police station and persuaded police to release the detainees, who had been working as guards for his party. But as the group was leaving, two policemen opened fire and shot Qahtan, Yawer added.

The two policemen were being investigated as suspects in the shooting, a police official said on condition of anonymity because he was not authorized to speak to the press.

Also Saturday, the U.S. military arrested five suspected Iranian-backed Shiite extremists accused in recent rocket attacks on Iraqi and American forces.

The military said it captured the five suspects in three separate locations in a largely Shiite neighborhood in eastern Baghdad, acting on intelligence information.

The extremists are suspected of links to the Hezbollah Brigades, a Shiite extremist group that the U.S. believes is backed by Iran. Tehran denies U.S. allegations that it is supporting violence in Iraq.

The U.S. military announced that a soldier died southeast of Baghdad when his vehicle rolled over, bringing the number of American servicemen killed since the March 2003 start of the war in Iraq to 4,174, according to an AP count.

Associated Press writers Sameer N. Yacoub in Baghdad and Yahya Barzanji in Sulaimaniyah contributed to this report.