Iraqi forces have formally assumed responsibility for security in southern Dhi Qar province. It is the second of 18 Iraqi provinces to pass to local control.
Iraqi forces took over Thursday from the Italian contingent of the Multi-National Force. Italian Defense Minister Arturo Parisi joined Iraqi Prime Minister Nouri al-Maliki in the handover ceremony at the regional capital, Nasiriyah.
In a statement, the U.S. Ambassador to Iraq Zalmay Khalilzad called the transfer "an important milestone" toward a stable Iraq.
But insurgent attacks and sectarian killings continued throughout Iraq Thursday. In Baghdad, gunmen attacked a police station in the city's upscale Mansur district and killed six officers.
In Geneva, the special U.N. investigator on torture Manfred Nowak said torture may be worse today in Iraq than during the regime of ousted president Saddam Hussein.
He spoke of allegations of torture at official Iraqi detention centers.
U.S. and Iraqi forces have been conducting a sweep of Baghdad neighborhoods to arrest suspected insurgents and death squads.
Iraq has seen a spike of violence in recent weeks, with hundreds of bodies found bearing the marks of torture.
A United Nations report released Wednesday said nearly 6,600 Iraqis were killed in July and August. The figure is much higher than the previous two months.
A top U.S. commander in Iraq, Major General William Caldwell said on Wednesday that he expects attacks to increase further during the Islamic holy month of Ramadan, which is expected to begin Saturday.
Some information for this report was provided by AP and Reuters.