American soldiers signed over their last military base to Iraqi officials on Friday with the U.S. troop pullout drawing to an swift end nearly nine years after the invasion that ousted Saddam Hussein.

The few thousand remaining U.S. troops are scheduled to leave Iraq before December 31, closing a U.S. military venture that cost the lives of nearly 4,500 U.S. soldiers and tens of thousands of Iraqis caught up in sectarian strife.

Iraqi and U.S. officials on Friday signed paperwork for the handover of Camp Adder with a ceremony marked by army bugle calls and the lowering of flags. Only about 4,000 American soldiers remain in the country, down from a peak of 170,000.

"We have turned the last page of the occupation," Hussein al-Asadi, an adviser for Prime Minister Nuri al-Maliki, said at the base, 300 km (185 miles) south of Baghdad.

Camp Adder, a former air base in southern Nasiriyah province, will be one of the last few handed over as troops head south to the Kuwaiti border, leaving behind them housing units, generators and other material they cannot take along.

In the last month Camp Adder had turned into a ghost town. A yard was filled recently with chairs, tables and furniture handed over to the Iraqi forces. Signing over the bases usually happens before the final transfer.

The more than 500 U.S. bases at the height of the war have been whittled to a handful with daily convoys of hundreds of trucks and U.S. military vehicles crossing southern Iraq into Kuwait.

U.S. soldiers ended combat missions in 2010 and have already handed over much of the security role to Iraqi forces, but the last troops pull out of an Iraq that is still confronting a stubborn insurgency and political uncertainty.

Many Iraqis welcome the end of the U.S. military presence but fret over whether Iraq's government will manage tense sectarian relations, a fragile political power-sharing deal and an economy in dire need of investment.

U.S. Defense Secretary Leon Panetta flew briefly into Baghdad on Thursday for a ceremony to officially end the war in Iraq, telling U.S. and Iraqi officials that the sacrifice was worth it to establish an independent, stable country.

Violence has fallen sharply since the days of the worst sectarian slaughter in 2006-2007, an uneasy political power-sharing government of Shi'ite Muslims, Sunni Muslims and Kurds is in place and foreign oil firms are helping Iraq ramp up production.

But tensions simmer close to the surface. Minority Sunnis who once ruled under Saddam are chafing against what they see as a majority Shi'ite-led government that has marginalized them outside of power-sharing.

Hundreds of police protected a provincial council building in restive Diyala province on Friday as about 500 Shi'ite protesters rallied for a third day against an attempt, by mainly Sunni politicians, to seek more provincial autonomy.

SENSE OF SOVEREIGNTY
Desire for more autonomy has been evident for years in Iraq's patchwork of sectarian, ethnic and tribal makeup, but the Diyala drive and a call from mostly Sunni Salahuddin province for more say are intensifying regional jostling as U.S. troops leave.

"The province is passing through a very critical moment with the U.S. military walking out," said teacher Talib Hassan, 35, protesting outside the Diyala council building. "The timing of this declaration of autonomy is just attempted rebellion."

In Falluja, the former heartland of an al Qaeda insurgency that suffered some of the most vicious fighting in the war, a few thousand Iraqis celebrated the withdrawal this week, with some burning U.S. flags and waving pictures of dead relatives.

Falluja became more than any other Iraqi city a symbol for the brutality of the war after the 2003 invasion. Some in Falluja still remember what they call there the 'resistance' to U.S. military incursions.

"The occupiers are leaving and so do the tanks, fighter-jets and rifles," Ahmed al-Alwani, the Imam of al-Raqeeb mosque said in speech at Friday prayers.

"Do you know why Falluja was first in celebrating the U.S. withdrawal? Because it was the first in resisting them."