The attack on a residential compound in Riyadh killed 18 people and injured over 100 others on Sunday evening.

The bombings came despite warnings from the American, British and Australian governments that an attack in the country was ripe.

The warnings were issued over a five week period, starting on 6 October when the US issued a statement saying ''known terrorist operatives'' were watching the movements of westerners in the kingdom.

Target

A further warning was issued last Friday, with the US stating that 'terrorists' were in an ''operational phase'' able to launch an attack at any time.

Last week a senior western diplomat admitted that ''a group linked to al-Qaida are in the final stages of planning a major terrorist attack. Frustratingly we didn't know the target or the timing.''

After Sunday's attack on the compound, the same diplomat said that he could not rule out that armed groups weren't planning to launch further attacks in the kingdom.

Security

Intelligence failed to predict
Sunday's bombing attack

Questions are being asked about the reliance on western intelligence in being able to thwart future bombings in Saudi Arabia and around the world.

The Saudis criticised the British government last month for failing to coordinate security warnings with Saudi officials.

For the Saudis the warnings undermine investor confidence in the kingdom and makes the government appear as if they have no control over security in the country.

Security analysts however insist that intelligence gathering is improving all the time, as is the monitoring and penetration of Islamist dissident groups in the kingdom, despite failing to prevent Sunday's attacks.

Experts believe that the bombing was aimed at undermining the Saudi leadership and showing the government that groups within the country had the means to strike at any time and at any target.