Iraq's defense minister on Wednesday insisted that the head of the country's major Al Qaeda front group was in custody, despite an online statement by the leader that he was still free.

Abdul-Qader al-Obeidi told lawmakers that the man captured on April 23, and later shown in a photograph displayed by the authorities, was Abu Omar al-Baghdadi, leader of the Al Qaeda dominated Islamic State of Iraq

On Tuesday, however, militant Web sites carried an audio message purportedly from al-Baghdadi mocking the Iraqi government and denying he had been taken captive.

The recording called to mind previous claims by Iraqis of captured terror leaders that were later found to be false.

"Everyone was surprised by the lies of the Green Zone leaders who claimed again that they detained me," the speaker said.

Rita Katz, the director of the U.S.-based SITE Intelligence Group which monitors such Web sites, said the voice seemed like that of the person previously identified as al-Baghdadi.

"It sounds as though it is the same individual," she told The Associated Press.

Al-Obeidi, however, pointed to the two-week gap between the message and the arrest, saying that was evidence of a power struggle in the group over who will succeed al-Baghdadi.

"The terrorists are having differences in naming his successor," he said, adding that the suspect in custody gave up information on insurgent cells in Baghdad and Mosul.

The U.S. military never confirmed al-Baghdadi's arrest and, in the past, has even questioned his role, saying he was simply an actor used by the terror movement to give an Iraqi face to an organization dominated by foreign Al Qaeda fighters.

Unlike some top jihadi figures, al-Baghdadi has never issued images of himself, releasing only audio messages.

It is also unclear whether he exerts real authority or is simply a figurehead.

Iraqi officials also have reported al-Baghdadi's arrest or killing before, only to later say they were wrong.

In 2007, Iraq's government reported that al-Baghdadi had been killed and released photos of what it said was his body. Later, security officials said they had arrested al-Baghdadi.

In both cases, the U.S. military said at the time it could not be confirmed. The reports turned out to be untrue.

Past arrests and killings of top insurgent figures, however, has done little to blunt the violence.

The days since the announcement of al-Baghdadi's capture have witnessed an increase in attacks.

On Wednesday, a senior anti-corruption official was assassinated on his way to work.

Ali Mohammed Kazim of the Public Integrity Commission was driving to his office in the northern Shaab neighborhood when a car blocked his path and gunmen armed with silenced pistols walked over and shot him dead, said police, citing eye witnesses.

The incident is similar to the early morning slaying of a high ranking traffic officer two days earlier.

Amid the occasional spikes of violence, however, the U.S. military has been moving forward in transferring bases to Iraqi forces ahead of a June 30 deadline to remove all Coalition forces from urban areas.

The U.S. Army handed over its base at the 6,000-year-old archaeological site of Ur in the south of the country to the Iraqi military in a ceremony Wednesday.

According to the Bible, Ur was the home of the Prophet Abraham. The ruins include a 4,000 year-old partially reconstructed ziggurat from the Sumerian period.

The presence of a U.S. base on one of Iraq's most significant archaeological sites prompted an outcry among international experts.