The leader of Al Qaeda (search) in Saudi Arabia (search) was believed killed in a raid in the capital Friday, hours after his group claimed the beheading of an American engineer, Saudi security officials said.

A U.S. official confirmed that Abdulaziz al-Moqrin (search) has been killed. The official spoke on the condition of anonymity because of the sensitive nature of the information.

To establish identities, one Saudi official said forensic tests would be conducted on three bodies of militants killed in a shootout in a downtown neighborhood shortly after the discovery of Paul M. Johnson Jr.'s (search) body.

A senior Saudi official in Washington said a second operation aimed at al-Qaida supporters or suspects was under way.

The killing of al-Moqrin, 31, would be a coup for the Saudi goverment, which has been under intense pressure to halt a wave of attacks against Westerners in the kingdom.

The Saudi-owned Al-Arabiya satellite station, which first reported al-Moqrin's death, said two other militants were also killed in the raid, and another was wounded and arrested. All three dead militants were on Saudi Arabia's list of most wanted men, security officials said, speaking on condition of anonymity.

Two suspects escaped, he said, said one Saudi security official who took part in the raid.

Al-Moqrin, who trained with Usama bin Laden (search) in Afghanistan, is believed to be the leader of the group calling itself Al Qaeda in the Arabian Peninsula, which claimed responsibility for Johnson's beheading.

Al-Moqrin's group has also claimed responsibility for most attacks against Westerners in Saudi Arabia in the past two months.