An attack on an oil refinery in Saudi Arabia poses the biggest challenge yet to the kingdom, writes John R Bradley An attack this week on an oil refinery in Saudi Arabia in which five Westerners, two Saudis and four militants were killed, is the kingdom's worst nightmare come true. It was the first terrorist assault on a petrochemical complex in the country. It came just weeks after the first direct targeting of a government building in Riyadh, when five people died. Reports of a Westerner's corpse being dragged through the streets of the industrial city of Yanbu, and militants firing in the air to urge others to join the fight, have horrified the Western expatriate community on whom the kingdom still largely depends to keep its vital oil industry working. Four of the Westerners killed were senior managers at the complex. The Swiss- Swedish engineering company ABB, employer of the slain Westerners, immediately announced it was evacuating all international staff and their families from Yanbu. Meanwhile, the US State Department referred citizens to its message of 15 April, saying: "Private American citizens currently in Saudi Arabia are strongly urged to depart." Last month, the US ordered non-essential diplomats out of Saudi Arabia. Such warnings, coupled with the ever-present threat of further instability, could hurt efforts to attract international investment and diversify Saudi Arabia's oil-dominated economy. Concerns about security have shot up since it was revealed that the Yanbu shooting was carried out by workers at the complex who had used their uniforms and passes to gain access to the guarded site. At least three of the attackers worked in the plant. "I've changed my attitude to the Saudis I work with," said Briton Abdullah Hussein, who works at the Yanbu oil refinery. "It makes me feel very uncomfortable that the workmates I've known for years could be a possible threat to me and my family," he told Al-Ahram Weekly. It was the third major attack on foreigners in the country. Saudi authorities have responded by saying they will crush terrorists. More than 50 died and hundreds were injured last year when Western-style compounds in Riyadh were bombed by Al-Qa'eda operatives. One of the attackers killed in the Yanbu violence was Abdullah Saud Abu Nayan Al-Sobaie -- No.10 on a list of the kingdom's 26 most-wanted terrorists. Jamal Khashoggi, adviser to the Saudi ambassador in London, said the gunmen were two brothers and their two uncles, all members of a local family. This may be the first instance of militants having successfully attacked an oil installation, but there has long been evidence that terrorists have infiltrated the ranks of Saudi Aramco, the world's largest oil company. US intelligence alerted officials in the summer of 2002 that they had intercepted conversations about sabotage among company employees. As a result, Al- Qa'eda sympathisers who tried to blow up Ras Tanura oil terminal were arrested. Al-Qa'eda has also infiltrated Saudi Arabia's military and security forces at the highest level, including those entrusted with the protection of Western residential compounds, American intelligence officials said after last year's 12 May Riyadh bombings. Worryingly, Yanbu residents said it took more than 90 minutes from the time they sounded the alert for security forces to finally engage the militants. The gunmen also fired on a McDonald's outlet and threw a pipe bomb at an international school. "I think this attack signals a change in tactics. The civil war is now on in Saudi Arabia, that's for sure," prominent Saudi columnist Mohamed T Al-Rasheed told the Weekly. A week before the Yanbu attack, Al-Qa'eda had also brought its terror to Jeddah, the city of Osama Bin Laden's birth, for the first time. Five militants were killed in a series of shoot- outs and an apparent suicide bombing. There is no small irony in the fact that the Hijaz region -- which includes both Yanbu and Jeddah -- has become a battlefield in the ruling Al-Saud's relentless confrontation with the terror network they unwittingly helped to create. As the gateway to the annual haj, Jeddah is the Kingdom's most cosmopolitan and diverse city. Jeddah is also where Osama grew up, graduating from its local university. Located in the city are a number of financial institutions accused by the US of having funded, or provided cover for the funding of, Al-Qa'eda. The headquarters of the Saudi Bin Laden Group is just two kilometres from the spot where the Jeddah violence occurred. Arguably the birthplace of 11 September and the war on terror, with last year's events the violence came full circle. Four of the militants killed in Jeddah were on a most-wanted list issued last year by the Ministry of Interior, a statement carried by the official Saudi Press Agency said, adding that the fifth suspect blew himself up. "All of the young people here are with the government for now," said Ahmed Al-Ghamdi, a 23-year-old student at Osama's former place of study, King Abdul-Aziz University. "We are frightened to go out. We want security more than anything else," he told the Weekly. The paradox is that while liberals in places like the Hijaz support the crackdown on Islamist radicals, they are also demanding speedier reforms, and are, in that sense, also turning against the Al-Saud. Last year, when a peaceful demonstration was planned in Jeddah to call for more democracy, the city became a virtual garrison town overnight. The army closed off whole districts, riot police lined the main streets, armed special security forces gathered outside the mosques and the secret police had cameras trained on all and sundry. Hundreds were arrested, many of whom were sentenced to prison and lashings. "Until the government realises that peaceful demonstrators are not the same as Islamist radicals, they will not get the widespread long-term support they need," said an American expert who has lived in Jeddah for almost 20 years. "Westerners here now have their suitcases packed, ready to leave," he added. The writer, a former managing editor of the Jeddah-based Arab News , is author of the forthcoming book Saudi Arabia Exposed: Princes, Paupers & Puritans in the Wahhabi Kingdom. His Web site is www.johnrbradley.comwww.johnrbradley.comi.