The Saudi government confirms the top al-Qaida terrorist in the royal kingdom Abdulaziz al-Muqrin was killed late Friday along with three of his associates. The body of decapitated American businessman has not yet been found. U.S. officials warn of security risks for Americans residing in Saudi Arabia.

Saudi government spokesman Adel al-Jubeir says Abdulaziz al-Muqrin and his three associates were responsible for the kidnapping and murder of American Paul Johnson. He also blames them for recent attacks on Western residential compounds and the murders of a British and a German national. He says 12 other suspects have been arrested.

Mr. al-Jubeir says the killing of the Al Qaida leader is, in his words, a major blow for the terrorist network in Saudi Arabia.

Mr. al-Jubeir told a Washington news conference security forces seized weapons and money during the assault in a central Riyadh neighborhood.

"They captured machine guns and ammunition, three rocket-propelled grenade launchers, 16 pipe bombs, fake IDs and approximately $45,000 in cash, mainly in Saudi rials," he said.

Mr. al-Jubeir says more than 15,000 security forces were involved in the manhunt for Paul Johnson's kidnappers. He says the forces are continuing their search for other terrorists.

"We are resolved to fight terrorism, those who fund and those who justify it," said Adel al-Jubeir. "We will show no mercy." The Saudi foreign policy advisor dismissed suggestions the murder of Mr. Johnson and attacks on U.S. interests in Saudi Arabia would damage bilateral relations. He says the two countries have been closely cooperating on counter-terrorism campaigns for more than a year.

In Riyadh, U.S. ambassador James Oberwetter offered his praise for Saudi efforts to eliminate terrorist networks.

"Good work is being done by the Saudis, but it will be some time before we achieve a comfort level that the situation has returned to normal," he said.

Mr. al-Jubeir says Saudi Arabia's Crown Prince Abdullah has talked with President Bush to bring him up to date on security operations.