Australian hostage Douglas Wood was freed in a military operation by Iraqi troops backed by U.S. forces, said officials Wednesday.

Iraqi militants in Baghdad have been holding Wood hostage since late April, and threatened to kill him if Australia didn't withdraw its troops from Iraq.

The 64-year-old civil engineer, a resident of California, is now under the protection of Australian troops in Baghdad, announced Australian Prime Minister John Howard.

"Mr. Wood was recovered a short while ago in Baghdad in a military operation that I am told was conducted by Iraqi forces in cooperation in a general way with force elements of the United States," Howard told Australia's Parliament on Wednesday.

"I understand that he is well. He's undergoing medical checks at the present time."

No details were available on the military operation that led to Wood's release.

Howard said the Australian government refused to give in to demands of the kidnappers, who called themselves the Shura Council of the Mujahedeen of Iraq. A team of diplomats, police and military personnel has been working on Wood's release.

"At no stage has a ransom been paid. At no stage has the government compromised its position in relation to our commitment to Iraq," said Australian Foreign Minister Alexander Downer.

He added that he phoned Wood's family, who he described as being "tremendously excited" at hearing the news.

Wood's release comes three days after French journalist Florence Aubenas and her Iraqi translator were released after being held hostage in Iraq for five months.