Jiddah, Saudi Arabia ? Lobbing grenades, militants invaded Jiddah’s heavily guarded U.S. Consulate on Monday, attacking staffers and others in the compound until Saudi security forces stormed in. Five compound workers and four attackers, none American, were killed in the attack, which was claimed by al-Qaida and showed how vulnerable Saudi Arabia remains to Islamic extremist violence.

The bold assault, the worst in the kingdom since May, suggested that a fierce crackdown waged by Saudi security forces has not completely put down al-Qaida in the native land of terrorism leader Osama bin Laden.

The group Al-Qaida in the Arabian Peninsula said the attack was part of its “war on the crusaders and the Jews …. (aimed at) getting them out of the Arabian peninsula. The Mujahedeen are continuing on their path … they will not weaken … but will be patient.”

In a statement posted on a militant Web site, the group said the attack had been named “the blessed Fallujah battle,” referring to the former insurgent stronghold in Iraq invaded last month by U.S. troops. It also said it was carried out by the “unit of the martyr Abu Anas al-Shami,” who was a spiritual adviser to Abu Musab al-Zarqawi, the most feared terrorist in Iraq. There was no way to confirm the claim.

President Bush said the attack showed “terrorists are still on the move,” trying to intimidate Americans and force the United States to withdraw from Saudi Arabia and Iraq. The U.S. Embassy in Riyadh and the consulate in Dhahran were closed to the public for two days, as was the Jiddah consulate. The Embassy urged the thousands of Americans in the country — many of whom already live under extraordinarily tight security — to “exercise utmost security precautions.”

Monday’s assault began when the attackers sneaked on foot behind an embassy car that was entering the consulate through a gate, then lobbed grenades at guards to take control of the gate area, said Brig. Gen. Mansour al-Turki, the Interior Ministry spokesman. The attackers also used incendiary grenades designed to create fires and to send up heavy smoke, he said.

Plumes of black smoke could be seen rising in the air shortly after the attack. About 20 minutes after fighting their way in, the attackers telephoned emergency services, claimed to be holding up to 17 people hostage and warned Saudi forces not to attack, said Adel al-Jubeir, foreign affairs adviser to Crown Prince Abdullah.

Those held at gunpoint were mostly either in the courtyard-like area to apply for visas, or were employees who worked in that area, a senior Saudi official in Washington said.

As the call was ending, Saudi security forces stormed the area and fought a short gunbattle, the official said. Al-Jubeir said the fight was over within three or four minutes, and the troops then worked for about three hours after that searching the compound to ensure it was secure. He denied earlier reports that the standoff lasted four hours.

Employees rushed into a safe area, and the attackers never made it inside the consulate’s buildings, al-Turki said. He denied anyone was held hostage but said the militants did attack those they came across in the courtyard area.

Smoke rises following an explosion in Jiddah, Saudi Arabia, after Islamic militants attacked the heavily guarded U.S. Consulate. Nine people were killed in the battle.