The group was discovered to have built up a cache of arms, including 55 hand grenades, 377 kilograms (829 pounds) of explosives, and 2,545 bullets of different calibers, as well as cash and various disguises.

The ministry said it was seeking “19 terrorists, 17 of them Saudis,” but added that it expected to add other names to the wanted list later. The two non-Saudis being sought are a Yemeni and an Iraqi with joint Kuwaiti-Canadian nationality.

Asharq Al-Awsat, a sister publication of Arab News, quoted a senior security official as indicating that the group had links with Al-Qaeda. “They had gone to Afghanistan,” he said, adding that their aim was to undermine the Kingdom.

The official also said the type of the explosives found by police was RDX, which has hugely destructive potential.

The ministry called on the public to telephone the nearest police station if they have any information which could lead to the suspects’ arrest, and warned anyone against giving them refuge.

The shootout started late Tuesday evening as police were searching for those responsible for a March 18 bomb incident which killed a Saudi in the capital’s Jazira district.

The gunmen’s getaway car broke down, but they were able to steal another vehicle at gunpoint and disappear into the teeming neighborhood.

Police discovered “55 hand grenades, 295 bullets, seven empty magazines, travel documents, identity cards and $72,957 cash” in the car, the ministry said.

A subsequent search of their hide-out turned up “377 kilograms (829 pounds) of explosives, four Kalashnikovs, three chests containing 2,250 bullets... 82 magazines (of bullets) and communications equipment.”

A search of another vehicle parked in the courtyard of the raided house in the Ashbeliya district, east of Riyadh, netted “three Kalashnikovs, wigs and other disguises.” Some of the individuals were leaving the house as security forces arrived, and were followed. It was at that point that the extremists opened fire and made their escape.

The US State Department said last week that it had received intelligence reports indicating “terrorist” groups may be in the final phases of planning attacks against the American community in Saudi Arabia.

The State Department warning came after an American working at a Saudi naval base was shot and injured. Washington has issued a new travel advisory warning its nationals against non-essential travel to the Kingdom, and urging private citizens here to consider leaving.

Meanwhile, Al-Majalla, a sister publication of Arab News, reports that Al-Qaeda is preparing a new attack in the United States on the scale of Sept. 11 after adopting a new operational structure which is impenetrable to US intelligence. “An attack against America is inevitable,” Al-Majalla quotes the militant network’s newly appointed spokesman Thabet ibn Qais as saying in an e-mail to the magazine.

Al-Qaeda has “carried out changes in its leadership and sidelined the Sept, 11, 2001 team”, the magazine quotes Ibn Qais as saying. “Future missions have been entrusted to the new team, which is well protected against the US intelligence services. The old leadership does not know the names of any of its members.” Ibn Qais mocks concerns expressed by Washington about a possible Al-Qaeda attack on its consulate in the Pakistani metropolis of Karachi, saying the network’s target is the United States itself.

“Of course, the US Consulate in Karachi is a US interest and a staging post for Federal Bureau of Investigation personnel in Pakistan, but it doesn’t necessarily constitute a pressing target. Striking it is not a priority for Al-Qaeda compared with the plans under way preparing a new attack in the United States on the scale of Sept. 11.”

The purported message from Al-Qaeda scoffed at recent press reports that US agents are hot on the trail of its leader Osama Bin Laden, whose whereabouts have been a mystery since the ouster of his Taleban sponsors in Afghanistan in late 2001.

“We keep our cool in the face of such reports, just as we do when the Americans say they have uncovered new Al-Qaeda plans or arrested our leaders,” Ibn Qais is quoted as saying.