Osama bin Laden himself is still believed to be hiding out in the border area between Afghanistan and Pakistan. But two of his key lieutenants, Saif al Adel and Mohammed al Masri, are known to be in Iran. Al Adel was once bin Laden's chief of security and al Masri ran the al Qaeda training camps in Afghanistan.
Both men played key roles in the 1998 bombing of two American embassies in Africa and have risen to the senior ranks of al Qaeda as more and more of its leaders are killed or captured. Officials say Iran is not serving as a base for al Qaed the way Afghanistan once did; there are no al Qaeda training camps in Iran and no rank-and-file fighters.
But a handful of senior al Qaeda leaders, including one of bin Laden's sons, now use Iran as a sanctuary, which, for the moment at least, is safe from American attack. At secret meetings in Geneva, the U.S. has demanded Iran turn over the al Qaeda leaders, but the Iranians have denied knowing anything about them.
"The repetition of such baseless claims ((concerning al Qaeda) cannot portray them as valid and credible," Iranian Foreign Ministry spokesman Hamid Reza Asefi said, according to the official Islamic Republic News Agency.
The Iranians insist they would arrest anyone even suspecting of having al Qaeda connections.
Faced with intelligence that Monday's bombings in Riyahd were only the first in a wave of al Qaeda attacks in countries stretching from East Africa through the Middle East and Central Asia, all the way to Malaysia and the Philippines, the State Department is directing all its embassies to be on a wartime footing.
There are even reports an al Qaeda operative named Abu Mousab Zarqawi, who has been blamed for the murder of an American diplomat in Jordan and is now believed to be in Iran, is plotting attacks against U.S. troops in Iraq.
There's also an unconfirmed new terror threat against Saudi Arabia – this time aimed at the country's chief commercial city, Jeddah.
The Saudis are giving such threats their full attention since Monday's attacks on three compounds for foreigners in Riyadh, which killed Saudi 34 people, including eight Americans and nine of the alleged bombers.
CBS News Correspondent Tom Fenton reports Saudi special forces were on the streets of the capital Friday acting as policemen.
Saudi businessmen are also privately very worried about the new threats and how they can be dealt with.
"We need the FBI to help us stop these acts," said one businessman, an astounding reaction, since Saudi pride is seldom this openly welcoming of American help.
FBI agents have arrived in Riyadh, but have not yet been seen at the attacked compounds.
Businessmen say that although the attacks against targets in Riyadh, the capital, are very serious, the threats against Jeddah, Saudi Arabia's equivalent of New York, would mean the heart of Saudi business is now being targeted, too.
Within hours of Monday's bombings, security specialists, working on behalf of Western business, were already inspecting the target sites. They are now analyzing the potential risks and assessing the consequences of continuing to do business in Saudi Arabia.
"It is going to be very important for Saudis to establish a credible investigation and to give those people confidence that they can stay in Saudi Arabia, do their jobs and be safe there," says Kevin Rosser, a consultant with Control Risks, a company that provides security analysis to companies in Saudi Arabia.
"If they fail to do that, then I think over the longer run, you are going to see an exodus of ex-pats and that is going to have a very bad effect on the Saudi economy," Rosser says.
U.S. officials have said the Saudis did not do enough to prevent Monday's suicide bombings.
But President Bush said Friday that Saudi Arabia is a friend and the two governments are working closely to find those responsible and stop future attacks.
"The best way to defend the homeland, the best way to secure the future of the American people is to find the killers before they strike us. And that's exactly what we're doing now inside of Saudi Arabia," Mr. Bush said.
The Saudi royal family underscored its newfound concern about the terrorist threat Friday by dispatching its chief foreign policy adviser to speak with foreign reporters.
Adel al-Jubeir said the Saudi government would seek to bring down al Qaeda.
"We're both in the cross-hairs of this organization. We have never had as close, or as strong, a cooperative effort between our two countries as we have now," al-Jubeir said. "Have we failed? Yes. On Monday, we failed. We will learn from this mistake, we will ensure it never happens again."
Saudi clerics, who are carefully guided by their government, widely condemned the attacks in Riyadh at Friday prayers. One leading cleric in Mecca, Islam's holiest city, said such attacks are "aggression, murder, terrorism and destruction."