More than 100 expatriate workers are to be evacuated from the oil refinery at Janbu, where five Westerners were killed by four Saudi gunmen who then drove around the Red Sea city dragging the naked corpse of one man behind their car and taking pot shots at American symbols, such as McDonald’s, Holiday Inn and the international school.

One of the Britons killed was Michael McGillen, from Stoke-on-Trent, Staffordshire, who was working for the multinational engineering company ABB.

Two Americans, an Australian and a member of the Saudi national guard also died in the shooting. The five men were working on a project to revamp the oil complex co-owned by Exxon Mobil and SABIC, a Saudi company.

Unlike previous suicide attacks against Saudi security targets and foreign compounds over the past year, this was the first time that militants have so brazenly turned the streets of a normally conservative Saudi city into scenes normally associated with neighbouring Iraq.

Crown Prince Abdullah, Saudi Arabia’s de facto ruler, vowed that the insurgency would be crushed with “an iron fist”, but his regime has so far failed to stamp out the spate of attacks, believed to be inspired by al-Qaeda and Osama bin Laden, the Saudi fugitive.

Confidence in the ability of the Saudis to tackle the problem was not boosted when Prince Abdullah blamed “foreign hands” and “Zionisim” for the attacks, which are widely believed to be the work of homegrown Saudi militants.

Three of the attackers were said to have been employees at the Janbu plant, which is run jointly by the American oil giants Mobil and Exxon. They smuggled in the fourth militant, identified in the local press as Abdullah Saud Abu-Nayan al-Sobaie, the tenth most-wanted terrorist suspect in Saudi Arabia. The men burst into the company offices, killing Michael McGillen and Michael Hardy, who was also working for ABB.

In a chilling reminder of the lynching of American contract workers in Iraq, the men were said to have then stripped the body of one victim, tied him to the bumper of their car and drove into the town. Children at the Ibn Hayyan Secondary School reported seeing four bearded men drive into the school car park firing into the air and shouting “God is great! God is great!” and “Come and join your brothers in Fallujah (Iraq).”

“I was shocked and terrified when I saw them. I just froze. I did not know what to do,” Rayyan, 18, said. “This is not right . . . This is un-Islamic.”

British and American consular officials who visited the site of the attack repeated advice for their citizens to leave the country.

The carnage was aimed at striking a blow to the Saudi economy and its reliance on expatriate workers, who make up one third of the country’s population. Janbu is a busy industrial centre with big petrochemical concerns that employ many Westerners.

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