Usama bin Laden (search) has a new henchman running his Al Qaeda terrorist network in the Persian Gulf, U.S. intelligence officials tell Fox News.

Abu Hazim al-Sha'ir (search) — a 29-year-old former bin Laden bodyguard from Yemen who is now living in Saudi Arabia — is believed to be the head of terrorist operations in the Gulf, U.S. officials said.

Al-Sha'ir, who also goes by the name Khalid Ali bin-Ali al-Hajj, had a close relationship with former Gulf chief of operations Khalid Shiek Mohammed. Mohammed is the alleged Sept. 11 mastermind who was captured by U.S. and Pakistani authorities in March.

Al-Sha'ir is believed to have played a major role in the May 12 bombing in Riyadh, Saudi Arabia, officials said.

U.S. officials said Al Qaeda has been shifting in recent months as newer operatives take leadership posts to replace bin Laden chiefs who have been killed or captured since the Sept. 11, 2001, terror attacks on the United States.

"Capable replacements appear to be emerging, many of whom have demonstrated their ability to see previously planned operations through to fruition," according to one U.S. intelligence document, reported by The Associated Press.

Al-Sha'ir is just one of the top Al Qaeda (search) leaders now at large, according to officials from U.S. counterterrorism agencies, who discussed intelligence on the terror network on the condition of anonymity.

Officials acknowledge there may be other emerging leaders they don't know about. The CIA and FBI, for example, did not learn that Mohammed was a top Al Qaeda figure until well after the Sept. 11 attacks took place.

Al-Sha'ir appears to be replacing Abd al-Rahim al-Nashiri, a key organizer of the USS Cole bombing and the 1998 East Africa embassy bombings, officials say. Al-Nashiri was detained in the United Arab Emirates in late 2002.

Al-Sha'ir is on Saudi Arabia's list of 19 most-wanted Al Qaeda operatives, listed under his real name of Khalid Ali Bin Ali Al-Hajj. But he is not on the FBI's list of the most wanted terrorists.

He is believed to have trained in Al Qaeda's Afghan camps in 1999 and later to have served in bin Laden's bodyguard, the AP reported. Before Sept. 11, he traveled frequently to the Arabian peninsula, to southeast Asia and to Afghanistan.

U.S. counterterrorism officials also tie him to the May 12 bombings of residential complexes in Riyadh and possibly to some Saudi-based planning of operations targeting the United States directly.

But there isn't hard evidence tying him to ongoing attacks on U.S. forces in Iraq, according to the AP.

Al Qaeda Disrupted After Sept. 11

Al-Sha'ir's emergence as a senior figure comes as Al Qaeda is struggling to deal with the losses of many of its pre-Sept. 11 operational commanders, including Mohammed Atef (search), Khalid Shiek Mohammed and Abu Zubaydah (search).

Atef was killed in a U.S. airstrike in Afghanistan in November 2001, and Mohammed and Abu Zubaydah later were captured separately in Pakistan.

The international hunt for such senior leaders is a key component of the U.S.-led war against Al Qaeda. For all the thousands of people who trained at bin Laden's camps, only senior leaders are thought to have the connections, financing and savvy to pull off major terrorist attacks.

"The loss of so many senior operational coordinators represents the elimination of a decade worth of terrorism planning experience. These individuals were, in large part, the guiding force behind the success of Al Qaeda's attacks," the U.S. intelligence report says, according to the AP.

Yet, officials acknowledge there may be other, emerging leaders they haven't identified. And several from Al Qaeda's old guard remain at large.

They include Ayman al-Zawahri (search), bin Laden's chief deputy, and Abu Musab Zarqawi (search), an associate of bin Laden who is now thought to be in charge of Al Qaeda operations inside Iraq.

U.S. officials believe two more, Saif al-Adel and Abu Mohamed al-Masri, are in Iran. But it is unclear if they are in some kind of Iranian custody or able to move and communicate at will.

Al-Sha'ir's presence in the Saudi kingdom is telling, said Vince Cannistraro, a former CIA counterterrorism chief.

"The whole locus of Al Qaeda, in terms of its power and its strength, has moved to Saudi Arabia," he said.

Other members of the organization are believed to be in Pakistani cities, and many of the arrests of key Al Qaeda operatives have taken place in those areas. Still others, including bin Laden himself and al-Zawahri, are thought to be in the remote region along the border between Pakistan and Afghanistan.

The U.S. intelligence report also notes the Saudi kingdom's importance to Al Qaeda.

"Saudi Arabia has always been Al Qaeda's primary base of popular and religious support and funding," the report says. "While not as permissive an operating environment as Afghanistan was, the kingdom offered enough acquiescence for Al Qaeda to actively recruit, obtain and store explosives and weapons, plan terrorist attacks, and fund raise."

U.S. officials say the Saudis have made significant strides in battling Al Qaeda within the country since the May 12 bombing.

Fox News' Bret Baier and The Associated Press contributed to this report.