In a fierce assault on Iraq, allied warplanes "scattered" a unit of the elite Republican Guard and blew up airfields, tanks and personnel carriers on Saturday, military officers said.

Iraqi anti-aircraft gunners shot down two U.S. warplanes - the first lost in two days - but Iraq's air force offered no resistance, American officials said. The U.S. Air Force searched behind enemy lines for its downed airmen.One Marine was killed and two were wounded, reportedly when their convoy was struck in Saudi Arabia by cluster bombs dropped by American warplanes.

On a day of little ground activity, the U.S. Army was inspecting hundreds of Bradley Fighting Vehicles, its premier armored infantry transport, for a transmission defect that could limit its speed to 12 mph.

The vehicle is designed to travel at speeds up to 38 mph, but 511 Bradleys, about one-fourth of all those in Saudi Arabia, may have the problem, according to an Army memo obtained by The Associated Press.

Unbowed by the relentless allied bombing raids and the recent defeat in the city of Khafji, Iraq vowed to use every means from "kitchen knives to weapons of mass destruction" to fight the U.S.-led multinational force.

Throughout the gulf, U.S. and allied warplanes took advantage of near-perfect weather to hit targets throughout Iraq and Kuwait on Saturday, the 17th day of the war and six months to the day since Iraq invaded Kuwait.

"The last 24 hours have been most satisfactory for the British forces and for our coalition partners," British Group Capt. Niall Irving said.

He said Tornado warplanes had made "devastating visits" to two Iraqi airfields that were being repaired after previous attacks. The ground-hugging Tornadoes dropped forty 1,000-pound bombs on each airfield, he said.

"The Iraqis have been doing a great deal of work to repair their airfields, and that's why we've seen fit to go back and visit them again in the last couple of nights," Irving told a briefing in Riyadh.

He said the air strikes also were taking their toll on the Republican Guard, Iraq's elite fighting unit in southern Iraq and Kuwait. In the face of the bombing raids, he said, "their movements don't seem to be particularly well coordinated" and their command and control is "not too hot."

But he added, "I'm not suggesting for a moment that this is a totally disorganized shambles out there because it isn't."

Irving said the Iraqi ground forces didn't appear to be preparing for another attack on Saudi Arabia. "There is no offensive posturing going on there, it's all defensive as far as we can ascertain."

Asked if the Iraqi ground forces were collapsing or in retreat, he said: "No, there's no evidence of them retreating at all that I know of."

Despite the attacks on the airfields and on the Republican Guard, and others over the weekend on bridges and fuel storage tanks, the Iraqi air force continues to sit out the war for the most part, Irving said.

"Just three of their aircraft managed to get airborne yesterday," he said. "Their mission appeared to be simply to take off and land again."

There were no air raids over Baghdad on Saturday morning, but before dawn there was a large explosion, probably caused by a cruise missile, according to Associated Press correspondent Salah Nasrawi. The site of the explosion and extent of damage could not be determined.

The U.S. military said the Air Force flew 2,600 sorties on Saturday, 300 more than the daily average.

In one such attack on the Republican Guard, he said, "We scattered about 300 vehicles and had fairly substantial kills in both APCs (armored personnel carriers) and tanks."

On Friday night, he said, warplanes hit another Iraqi Scud missile site.

He said the decline in Iraqi Scud missile attacks on Saudi Arabia and Israel in each week of the war suggests that the allies are successfully wiping out the enemy's fixed and mobile rocket launchers.

Scud attacks resume

Hours later, Iraq launched missiles at Israel and the Saudi capital, Riyadh. The Scud over Riyadh was hit by a U.S. Patriot missile, but fragments landed on a residential neighborhood, damaging apartment buildings and causing two minor injuries, police said. No damage was done in the Israel attack.

A second missile was fired from western Iraq about five hours after the first attack, said Brig. Gen. Nachman Shai. No damage was reported.

Israeli officials say Iraq still has at least 15 Scud launchers, and sources in the Jewish state say Israel's military is considering a plan to use commandos to destroy Scud launchers and other targets in western Iraq.

Two U.S. warplanes were shot down by anti-aircraft fire on Saturday, and an American serviceman was killed, apparently by friendly fire, Marine Maj. Gen. Robert Johnston said.

The planes - an A-10 and an A-6 - apparently were shot down by anti-aircraft artillery, Johnston said.

The latest losses bring to 15 the number of American planes downed in combat. Five British planes, one Kuwaiti warplane and one Italian jet have also been downed since the Persian Gulf war began Jan. 17.