ABU DHABI ø A new U.S.-trained Saudi counter-insurgency unit has succeeded in releasing more than 50 hostages held by Al Qaida, but three of the four terrorists escaped.

The Saudi National Guard unit employed four U.S.-origin CH-47 Chinook heavy-lift helicopters to land about 40 commandos on the roof of a Western housing compound near Khobar and battled Al Qaida insurgents in an early-morning raid on Sunday. The Saudi commandos succeeded in freeing Arab and Western oil workers taken hostage by the insurgency group.

The number of casualties remain unclear, Middle East Newsline reported. The Saudi Interior Ministry said 22 people were killed, including an American, a Briton, an Egyptian, three Filipinos, eight Indians, an Italian, a Swede, two Sri Lankans, three Saudis and one South African.

The ministry said the insurgents failed in their attempt to bring a vehicle full of explosives into the compound.

The Interior Ministry said only one of the four Al Qaida insurgents ø described as the ringleader and a leading fugitive ø was captured. The arrested fugitive was identified as Nimr Al Baqmi.

The ministry said three Al Qaida insurgents commandeered a car and escaped in the direction of Dammam, 10 kilometers north of Khobar. The insurgents were dressed in Saudi military uniforms and used the hostages as human shields.

"Security forces wounded the leader of the group and arrested him, one of the most-wanted," the ministry said in a statement. "The three others, one of them wounded, fled from the [housing] complex."

The new Saudi commando force was said to have been established after the Al Qaida attack on Western targets in Riyad in May 2003. Diplomatic sources said the force ø composed of veteran Saudi combatants ø was trained and equipped by the United States in skills employed by U.S. Special Operations Forces. The United States has been asked to upgrade the National Guard in a proposed $900 million contract.

Officials said other Saudi security forces tried twice to storm the Oasis compound. In one attempt, the forces withdrew after discovering bombs planted by the insurgents.

But at about 5:30 a.m., the National Guard arrived with heavy-lift helicopters and about 40 commandos descended onto the roof. For the next 90 minutes, the commandos battled the Al Qaida insurgents throughout the vast compound and office complex. Officials said two commandos were killed and another eight were injured.

Saudi officials said the new commando unit was trained and directed by the U.S. military. But they denied a report in the Kuwaiti daily Al Watan that U.S. marines participated in the rescue operation.

The commando force was backed by another special unit located outside the walled compound. In all, about 200 special forces members ø including sharpshooters ø were outside the compound in search for insurgents trying to escape. The special forces came from Saudi Army and Navy.

The U.S. embassy said its personnel has been advised not to leave the so-called diplomatic quarter in Riyad until further notice. An embassy statement said the movement of American personnel at the U.S. consulates in Dhahran and Jedda have also come under similar restrictions.

"The U.S. Mission in Saudi Arabia wishes to advise the American community that on the morning of May 29, 2004, terrorist attacks were carried out against at least three Western targets in the city of Al Khobar," the U.S. embassy said in a statement. "Foreign nationals, including Westerners and Saudi citizens were killed in the attacks. In light of the terrorist attack in Yanbu on May 1, 2004, and this latest attack in Al Khobar, the embassy reiterates its previous warning strongly urging American citizens to depart the country."