Saudi Arabia has moved to reassure the world about its security regime after the latest savage attack by Islamic militants against foreign oil workers.
Police have set up roadblocks in a bid to catch the escaped gunmen
Extra police guarded possible targets as the hunt widened for three men who fled after a 25-hour siege in Khobar.
But grief turned to anger in expatriate circles amid accusations that the men cut a deal with police to escape after killing 22 people on Sunday.
Saudi officials have said their main priority had been to save lives.
The authorities sent commandos in to end the siege after the attackers had already started killing non-Muslim captives.
But one captive reportedly said they let the attackers go free after they threatened to blow up themselves and 41 remaining hostages.
Another witness quoted by the French news agency AFP said the gunmen fled wearing military uniforms, raising further queries about possible collusion.
A fourth militant, the alleged leader, was wounded by security forces and captured. Saudi authorities have not named him but they told the BBC he trained in al-Qaeda camps in Afghanistan.
1. Al-Khobar Petroleum Centre: Four gunmen arrive at 0715 Saturday, shoot at guards, enter building and fire at employees.
2. Arab Petroleum Investments Corp: Gunmen shoot British employee dead in his car at gate.
3. Oasis compound: Gunmen enter compound and take about 50 people hostage on sixth floor of hotel building. At 0530 on Sunday, Saudi forces land on roof and storm building. Nine hostages are found dead, 41 are released. Three militants escape, one is arrested.
Oil prices jumped more than a dollar a barrel amid uncertainty about security in Saudi Arabia, the world's biggest producer.
Petroleum exporting countries will meet on Thursday to discuss cooling high prices that were already threatening global economic growth.
Unease over the increasing frequency of attacks on foreigners has caused some companies and employees to consider whether to relocate from Saudi Arabia's oil-producing Eastern Province to the nearby island state of Bahrain.
Bahrain offers many more freedoms to foreign workers, including alcohol and cinemas, and fewer restrictions on female residents.
It has also avoided the kind of radical Islamist ideology thought to have triggered militant attacks in Saudi Arabia.
Foreigners make up the majority of the workforce in Eastern Province. Many enjoy affluent lifestyles that would not be available to them back home and past attacks have not triggered any mass exodus.
However, correspondents say this time it might be different.
Westerners in Khobar quoted in the media expressed particular concern that the attackers managed to enter a compound that was meant to be heavily guarded.
"What can expats do more than we're doing?" a US oil company employee told Reuters.
"Our security is in the hands of our companies. We all live in compounds and look at what happened."
Residents of the Oasis compound, where the siege took place, said the militants separated Muslims from non-Muslims, some of whom were killed in cold blood. Other victims were reportedly mutilated.
An audiotape posted on an Islamic website claimed the attack for al-Qaeda. "We will cleanse the Arabian peninsula of infidels," the tape said.
Most of the dead were Asians, including eight Indians, three Filipinos and two Sri Lankans. Three Saudis also died and one citizen each from Egypt, Italy, Sweden, South Africa, the UK and US.