Saudi Arabia was thrown into its own war on terror just more than a year ago, when suspected al-Qaeda militants launched triple suicide bombings in the capital Riyadh.
By Oliver Conway
Then, the killing of 35 people in attacks on compounds housing foreigners was seen as a wake up call to the Saudi authorities, who had been accused of going easy on Islamic militants in the hope of avoiding trouble.
There have been a number of attacks on foreigners' residences
A series of blasts targeting Westerners in 2001 had been blamed on British workers involved in the illegal alcohol trade. They were later released.
But following the attacks in May 2003, the authorities launched an unprecedented crackdown.
Six months later, the militants struck again at another residential compound killing 17.
In April this year, the Saudi authorities themselves became targets of several attacks, including a car bombing at the headquarters of the security forces.
And then this month began with grisly reports of a dead Western engineer being paraded through the streets.
He was one of at least six people killed in a shooting spree in the Red Sea port of Yanbu.
It was the first known attack by anti-Western groups on an oil facility in Saudi Arabia, and had knock on effects on the oil price.
Officials sought to portray that as an isolated incident, but Saturday's attacks also targeted the oil industry.
And they are likely to increase the exodus of foreign workers and their families from the kingdom.