A bomb near the northern Iraq city of Kirkuk has killed two police officers and injured at least two others.
The roadside bomb exploded when a police patrol passed on the outskirts of Hawijah, 45km (30miles) west of Kirkuk.
Military officials told AFP news agency that US and Iraqi forces had arrested 30 suspects following the explosion.
Meanwhile, the bodies of two US crew killed in a helicopter crash in western Iraq have been found.
The Blackhawk helicopter crashed into a waterway on Tuesday in Anbar province.
The US military said in a statement the crash was due to malfunction and was not related to enemy action.
Yesterday, a suicide bomb attack at a market in the southern Iraqi city of Najaf killed at least 35 people and injured more than 90 others.
The attack occurred near the Imam Ali shrine, one of the most sacred Shia Muslim sites. A Sunni insurgent group claimed it had carried out the bombing.
UN to stay
In a separate development, the United Nations Security Council announced it would be extending its mission in Iraq for another year.
The current mandate of the 400-strong mission was due to expire Friday.
The Iraqi Foreign Minister, Hoshyar Zebari, had earlier written to the UN Secretary General, Kofi Annan, requesting the extension.
Mr Zebari said while the political transition had come to an end, there was much work to be done to rebuild Iraq "for the benefit of this and future generations of Iraqis".