The blasts destroyed villas and apartments
The Saudi authorities say at least 29 people were killed and nearly 200 injured in apparently co-ordinated suicide bomb attacks against Western targets in the capital Riyadh.
Several Americans and a number of other foreigners - including two Filipinos - are believed to be among those who died in the attacks which came only hours before a visit to the city by US Secretary of State Colin Powell.
The dead also included nine suspected bombers, the Saudi Interior Ministry said.
Riyadh bomb victims
Source: Saudi Interior Ministry
Earlier US figures suggested that up to 10 Americans had been killed.
The attackers - believed to be members of Osama Bin Laden's al-Qaeda network - drove cars packed with explosives at three foreign housing compounds, detonating them with devastating effect.
A fourth blast was reported to have targeted the headquarters of a joint Saudi-US company, but caused no casualties.
US Secretary of State Colin Powell, who went ahead with his visit, said the "cowardly" operation bore all the signs of the al-Qaeda network.
"Terrorism strikes everywhere and everyone," he said.
"It is a threat to the civilised world."
Later, touring the Vinnell housing compound in Riyadh where a number of Americans were killed, Mr Powell told journalists that US experts would soon arrive to help the Saudi investigation into the bombings.
The attacks come two weeks after the US announced it was withdrawing most of its troops from Saudi Arabia, where they were deployed during the 1991 Gulf War.
Saudi Arabia is the birthplace of al-Qaeda leader Osama Bin Laden and 15 of the 19 men suspected of carrying out the 11 September suicide attacks on New York and Washington.
Russian President Vladimir Putin has said the suicide attacks in Saudi Arabia and Chechnya earlier on Monday were linked and bore the same imprint.
US Ambassador to Saudi Arabia Robert Jordan said that, at one of the compounds attacked, at least 12 homes and 16 apartment complexes had been destroyed.
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"There is great concern over the possible injury and loss of life in that particular compound," he said.
The second compound attacked was a residential apartment building for single men working as defence contractors which was "very seriously damaged by an explosion that made it all the way into the building", he said.
Nearly 200 people were injured
The third compound was less seriously damaged as the bomb exploded at the gate rather than inside the premises.
In one of the attacks, gunmen driving a black sedan are reported to have shot their way into the residential compound.
Security officials said the car, packed with explosives, crashed through the gates of the compound and was then detonated.
The force of the explosion shook nearby buildings and windows, witnesses said.
Mr Powell, who went to Saudi Arabia as part of a Middle East tour, was hoping to gain support in Riyadh for a new US-backed peace plan to end the Palestinian and Israeli unrest.
He was greeted on arrival by Saudi Foreign Minister Prince Saud al-Faisal, who
has promised to co-operate with the US in its war on terror.
The Saudi ambassador in London, Turki al-Faisal, said some of those involved in the Riyadh attacks were members of a fugitive group of 19 suspected al-Qaeda sympathisers who had disappeared from the city on 6 May.
American residents have been advised by the US embassy in Riyadh to stay at home and "away from windows and doors".
Workers from a US firm which helps trains the Saudi National Guard were reported to among those injured.
The Associated Press news agency said the fourth attack was aimed at the headquarters of the Saudi Maintenance Company, also known as Siyanco.
Foreign workers in Saudi Arabia
More than five million work in all areas of economy
Most from Asia, Philippines and other Arab countries
US citizens: 30,000
UK nationals: 30,000
On 1 May, the US State Department warned American citizens against non-essential travel to Saudi Arabia, citing intelligence that terrorist groups might be in the "final phases" of planning attacks against the American community there.
In recent months there have been a number of attacks on Western targets in the conservative Arab kingdom, including a string of shooting attacks against employees of western defence contractors in Saudi Arabia.
But British firm BAE systems, which has 2,500 workers in the kingdom, said the company would remain in Saudi Arabia in spite of the attacks.
A spokesman said: "BAE systems has been in Saudi for 35 years and has no plans to pull out now."