The terrain toward the foot of the Arabian Peninsula is unforgiving: jagged, rocky hills and barren deserts that make life difficult but smuggling easy. Handguns, machine guns, shoulder-launched rockets, plastic explosives, all styles of weapons are the contraband of choice.
The pace of smuggling into Saudi Arabia from neighboring Yemen has quickened in recent times. That has authorities here worried because the increase coincides with a rash of killings, shootings and bombings aimed at both Westerners and local Saudi officials.
In a country where weapons reportedly are common and the people increasingly hostile to the West, and with the knowledge that Al Qaeda cells are operating here, there is widespread fear that a U.S. invasion of Iraq would spark an outbreak of terrorist strikes.
"Al Qaeda has the ability to commit spectacular acts here," said a Western security expert with close ties to international intelligence agencies and years of experience in the Middle East. "Thousands of people have weapons."
The strikes might be simple and random, such as an attack on a Westerner stopped at a traffic light. That's how Robert Dent, 37, a British citizen with two young children, was killed last month -- shot in the head and chest.
Or they could be of the Sept. 11 variety, with mass casualties, such as the downing of a passenger jetliner with missiles. Authorities say they have found shoulder-launched surface-to-air missiles in the kingdom, and they expect that more are hidden and ready for use. Terrorists with missiles tried but failed to shoot down an Israeli charter jet taking off in Kenya last fall.
"There are many indications that terrorist groups are looking at a U.S. attack against Iraq as a convenient trigger" for a strike in Saudi Arabia, said a Western diplomat based here who requested anonymity.
Saudi officials fear that a terrorist attack could undermine their regime and at the least cause Westerners to flee, hurting the economy by scaring away foreign workers and investment.
The environment has become so tense that Canada has ordered families of its embassy employees to return home. The American telecommunications equipment maker Lucent Technologies has issued a mandatory evacuation call for all Western dependents, nearly 300 families in all. The U.S. and British embassies have issued an "authorized departure," which is voluntary, for nonessential employees and family members. Many more companies and embassies have not yet made the call to leave, but all are paying close attention to current events.
Authorities can't say for sure how extensive Al Qaeda's reach is in Saudi Arabia or the region, but government officials, diplomats and security experts have said the terrorist network has active members here and in other Persian Gulf nations. Saudi officials declined repeated requests for comment, but the government says that it has put 90 Saudis on trial for alleged links to Al Qaeda and that 250 of its citizens are under investigation. Recently, it has stepped up internal security efforts in both dramatic and subtle ways.
Saudi newspapers, for example, have largely stopped referring to suicide bombers in the Palestinian-Israeli conflict as martyrs, as part of a concerted effort to stop motivating recruits. Men who have been to Afghanistan in the last few years are being questioned by authorities and in some cases held. And Saudi security agents have begun locking up those who inspire hate and who call on people to commit crimes in the name of religion.
"The new thing is to go after the motivators," said Jamal Khashoggi, deputy editor of the English-language Arab News in Jidda. "Even though they are not involved in the violence, the ideological link is dangerous enough."
The crackdown has been problematic for the kingdom, politically and strategically. The Western-leaning government does not want to be seen as doing the bidding of the U.S., especially at a time when anti-American sentiment is rising on the street in reaction to the Iraq crisis and the Israeli-Palestinian conflict, and it does not want to create an environment that will inspire more terrorism recruits. In fact, security analysts believe that Al Qaeda has grown so frustrated with the crackdown that it has tried to step up its strikes within the kingdom.
The suspect arrested in connection with the Feb. 20 shooting of Dent told investigators that he went to a supermarket called Panda because it was frequented by foreigners. Sources said the suspect first considered shooting a man who was shopping with a woman and a child. Then he decided on Dent.
The U.S. Embassy informed Americans here that Dent's killing was "a terrorist act directed at a Westerner selected as a target of opportunity." The embassy also said the suspect "has associations with known terrorist elements."
By itself, the killing of Dent might be written off as a hate crime, but the strikes against Westerners and others have been piling up. Just last month: A deputy governor was shot to death in Al Jawf province in the north; a van full of Egyptian and Philippine doctors and nurses was sprayed with gunfire, though no one was injured; a Briton suffered minor injuries when he was shot while driving in Riyadh, the capital; an Australian man was fired on while jogging in the southern town of Khamis Mushayt; a McDonald's restaurant in Eastern province was the target of an attempted firebombing.
The events shocked a nation that bases its legal system on the Koran and prides itself on being free of street crime.
"Saudi Arabia, so long held up as a place of great safety for all, now has to face up to the brutal reality of so much of the rest of the world," the Arab News wrote shortly after Dent was killed, in a striking admission rarely seen here. "An age of innocence has gone."
More troublesome are recent arrests that suggest the problem has soaked deep into the fabric of the country. Authorities in the holy city of Mecca arrested seven young men, some of them high school students, on suspicion of belonging to outlawed groups.
Last year, officials arrested several Saudi employees of Saudi Aramco for plotting to sabotage the state-owned oil company's computer network. Even more damning, according to security experts in the kingdom, was the discovery last year that border guards had conspired with would-be terrorists to smuggle guns and explosives into the country from Yemen.
The Yemen connection is a major problem. Yemen's borders are nearly impossible to seal, with rocky, barren mountains near the coast and deserts stretching across a plain to Saudi Arabia. Arms smuggling has mushroomed, according to a high-placed government official from the region, who said many Saudis are paying top dollar in Yemen to secure weapons. The official said authorities are certain that some weapons are being purchased for terrorists.
"They are offering $1,000 for a weapon worth $100," said the official, who spoke on condition he not be identified.
In some cases, the official said, arms merchants are loading mules and camels with weapons and sending them unaccompanied across the border. If the animals are not caught, they are met on the other side by Saudi dealers.
Even as the U.S. declares success against the top levels of Al Qaeda -- such as the recent arrest of Khalid Shaikh Mohammed, the alleged architect of the Sept. 11 attacks -- authorities here say the terrorist network has become so diffuse and fractured that individual cells pose serious threats throughout the Persian Gulf region.
Security experts point to a suspected attack plot that was foiled last spring in a gulf state as an example of the kind of strike terrorist groups have tried -- and may try again. Details of the incident were disclosed under the condition that the names of the country and the individuals involved not be revealed.
The plot was uncovered when an American former narcotics agent living and working in the Middle East was shopping in two of the largest malls in the region. Over a two-day period, the former agent -- trained in surveillance -- noticed groups of men who were clean-cut and well-built and carried themselves like paramilitary fighters. They seemed to be staking out the malls, he said.
"It just looked wrong," he said. "They were cleanshaven men walking in military style, and they weren't looking at girls or shopping."
He contacted local law enforcement. A short while later, counter-terrorism authorities detained about 50 men suspected of planning to attack the malls, said a security expert with firsthand knowledge of the case. The target apparently was Westerners, but the goal was to undermine the local economy and thus the government.
Saudi Arabia's relationship with Al Qaeda dates back many years, to the days when the country's intelligence service worked closely with the Taliban government in Afghanistan.
The kingdom was one of only three countries, along with Pakistan and the United Arab Emirates, to recognize the militant Afghan regime. The Saudi government looked to the Taliban as a Sunni Muslim bulwark against neighboring Iran, which is mostly rival Shiite Muslim, and poured hundreds of millions of dollars in aid and services into Afghanistan, all while that country's leadership was providing a haven to Osama bin Laden and his followers in Al Qaeda.
The Sept. 11 attacks caught the Saudis off guard. Deep suspicion, even rejection, greeted the suggestion -- driven in part by the fact that 15 of the 19 hijackers were Saudis -- that the country's system had played any role in nurturing, inspiring or financing terrorism.
But over the last two years, authorities say, Saudi Arabia has recognized some of its errors -- perhaps not directly, but implicitly -- and has worked closely with U.S. intelligence services to combat terrorism.
"The Saudis have done a great job," said the Western security expert. "That has gotten Al Qaeda very angry at them. They have wrapped up lots of cells. Lots of people are in jail."
But it is a complicated situation for the Saudis. They can try to stop big, organized terrorist strikes, but they are largely helpless in heading off individuals acting on their own and striking at so-called soft targets, such as supermarkets and schools. Security experts, diplomats and civic leaders agree that for now, the number of people seeking to strike is a small percentage of the population.