Australia, a staunch U.S. ally and one of the first countries to commit troops to the Iraq war five years ago, ended combat operations there Sunday, a Defense Department official said.

Australian Prime Minister Kevin Rudd was swept into office in November largely on the promise that he would bring home the country's 550 combat troops by the middle of 2008.

Rudd has said the Iraq deployment has made Australia more of a target for terrorism.

The combat troops are expected to return home over the next few weeks. Local media reports said the first of the soldiers had already landed in Australia on Sunday afternoon.

Several hundred other troops will remain in Iraq to act as security and headquarters liaisons and to guard diplomats. Australia will also leave behind two maritime surveillance aircraft and a warship to help patrol oil platforms in the Gulf.

The troops on Sunday held a ceremony that included lowering the Australian flag from its position over Camp Terendak in the southern Iraq city of Talil, the official said, speaking on condition of anonymity as required by the Defense Department.

The soldiers, as well as 65 army trainers, were stationed at Talil, about 185 miles south of Baghdad, and were responsible for providing security training for Iraqi forces, as well as reconstruction and aid work. They have been on standby to offer backup to Iraqi forces in the south for the past two years.

In February, the head of Australia's defense force, Air Chief Marshal Angus Houston, told a Senate inquiry that the troops were no longer needed in Iraq.

Rudd remains committed to keeping Australia's 1,000 troops in Afghanistan.