The al-Hamra blast destroyed apartments and villas
The United States has criticised Saudi Arabia for not doing enough to protect Westerners in compounds targeted by suicide bomb attacks in the capital, Riyadh, which killed at least 34 people.
US Ambassador to Saudi Arabia Robert Jordan said Saudi officials had not responded quickly enough to recent US requests to improve security at the attacked compounds.
"We continue to work with the Saudis on this, but they did not, as of the time of this tragic event, provide the additional security we requested," Mr Jordan said in an
interview with CBS television.
The Saudi Foreign Minister Prince Saud al-Faisal said 15 Saudi nationals carried out the bombings and admitted there were security lapses.
He said: "The fact that the terrorism happened is an indication of shortcomings and we have to learn from our mistakes to improve our performance in this respect."
But Prince Saud also said he was not aware that the American Embassy had asked for, but did not get, extra security at one of the targeted compounds.
Meanwhile, Western and Saudi officials have warned of the danger of more attacks following the blasts at the al-Hamra, Jadawal and Vinnell compounds on Monday.
The US State Department said there was a "potential of further terrorist attacks", while the British Foreign Office described the threat as "high".
Saudis 'must do more'
The US and Saudi Governments have blamed Osama bin Laden's al-Qaeda network for the attacks.
Riyadh bomb victims
Source: Saudi Interior Ministry
The BBC's security correspondent Frank Gardner says Saudi authorities are coming under intense pressure to confront the threat from al-Qaeda more effectively.
White House spokesman Ari Fleischer said Saudi Arabia "must deal with the fact that it has terrorists inside its own country".
He said the US would push Saudi Arabia to "do more" in the fight against terrorism.
The United States has sent a team of Federal Bureau of Investigation (FBI) agents to gather evidence alongside Saudi police, while Britain has sent two specialist teams to Riyadh to help with the investigation.
The US has urged all US citizens to leave Saudi Arabia immediately, while the UK has authorised its non-essential diplomats in the kingdom to return home if they want to.
Buildings in the al-Hamra compound were devastated by what appeared to be a co-ordinated strike, with some witnesses saying the assault began when guards opened a security gate to let another vehicle leave.
The victims include 11 Westerners - mainly Americans - seven Saudis and several Jordanians, as well as the nine suspected attackers, who shot their way past armed guards and rammed vehicles packed with explosives into the compounds.
The British Ambassador to Saudi Arabia, Sir Derek Plumbly, said two Britons were unaccounted for, although it was not clear whether one of these was a Briton reported dead earlier on Wednesday.
Ambassador Jordan was quoted as saying that al-Hamra compound was about a block away from a house where Saudis seized explosives and ordnance a few days before the bombing.
Saudi Arabia's Crown Prince Abdullah, the kingdom's de facto ruler, said the attacks had been carried out by "criminal butchers" who would be punished in hell for their actions.
'Victim of terror'
Analysts say Saudi officials have been eager to rebut criticism by some US officials that they have allowed al-Qaeda members to operate.
Our security correspondent says the US is worried about the strong possibility that the Saudi security apparatus has been penetrated by al-Qaeda sympathisers.
The Saudi Interior Ministry said nine of the bombers were connected to a group of 19 al-Qaeda members who escaped from police custody following a shoot-out in Riyadh on 6 May.
Saudi Arabia has been embroiled in the fight against international terrorism since it emerged that 15 of the 19 men suspected of carrying out the 11 September, 2001, suicide attacks on New York and Washington in 2001 were Saudis.
The desert kingdom has since striven to portray itself as a victim, rather than a harbourer, of terrorists.
"Ironically it was the 15 Saudis who did what they did in America and 15 Saudis who did what they did in Saudi Arabia," said Prince Saud.
"Nobody could accuse us of being responsible for attacking our own country," he said.