A "science project" of a rocket launcher forced the U.S. occupation authority to retreat from its main hotel Sunday, after a barrage by the Iraqi resistance that killed an American colonel, wounded 18 other people and sent scores of U.S. officials scurrying for safety, including the visiting deputy defense secretary.

Paul Wolfowitz (search), the shaken-looking but unhurt Pentagon deputy, said the strike against the Al Rashid Hotel (search), from nearly point-blank range, "will not deter us from completing our mission" in Iraq.

The assault was likely planned over at least the past two months, a top U.S. commander said, as the insurgents put together the improvised rocket launcher and figured out how to wheel it into the park just across the street from the hotel.

The effect of the 6:10 a.m. volley of rockets was dramatic: U.S. officials and officers fled from the Al Rashid, some still in pyjamas or shorts to a nearby convention center. The concrete western face of the 18-story building was pockmarked with a half-dozen or more blast holes, and shattered windows in at least two dozen rooms.

The modern, 462-room Al Rashid, housing civilian officials of the U.S.-led Coalition Provisional Authority and U.S. military personnel, is a symbol of the occupation. The assault pointed up the vulnerability of even heavily guarded U.S. facilities in Iraq, where American forces sustain an average of 26 lower-profile attacks daily, and where Wolfowitz had come to assess ways to defeat the stubborn 6-month-old insurgency.

More than 15 hours after the rocket fire and after U.S. security officials flooded the neighborhood, two explosions went off in the same downtown area. An Iraqi policeman said an assailant fired a rocket-propelled grenade at a U.S. convoy next to the al-Mansour Hotel, about a mile away from the Al Rashid. He said there were no casualties.

A day earlier, a rocket-propelled grenade had forced down a U.S. Army Black Hawk helicopter north of Baghdad, the 4th Infantry Division confirmed Sunday. The incident occurred just hours after Wolfowitz left that area on the second day of his three-day visit. One soldier was injured.

The U.S. command said the wounded included seven American civilians, four U.S. military personnel and five non-U.S. civilians working for the coalition. Two Iraqi security guards also were hurt. The command did not immediately identify the dead American, but Wolfowitz said he was a U.S. colonel.

A senior FBI official said the bureau, the Defense Department, the State Department and Iraqi police were all involved in the investigation. Wolfowitz and his aides were very close to the area of the hotel that was struck, but there was no indication the attack was directed at Wolfowitz, the Pentagon said.

Brig. Gen. Martin Dempsey of the 1st Armored Division (search) said he believed the insurgents timed the attack with the lifting this weekend of an overnight curfew in Baghdad and the reopening of a main city bridge.

"Any time we demonstrate a return to normalcy, there are those who will push back at that," Dempsey, who is responsible for security in Baghdad, told reporters.

Iraqi police said the attacker or attackers, in a white Chevrolet pickup, drove to the edge of the city's main Zawra Park and Zoo, just 400 yards southwest of the hotel, towing what looked like a portable, two-wheeled generator.

A police commander, who spoke on condition he not be named, said that when security guards approached, the assailants drove off, but rockets within the blue trailer apparently had been set to fire via a timer and suddenly ignited, flashing toward the hotel, a clear shot looming just over the treetops.

"When he saw us, he fled," guard Jabbar Tarek said of the driver. The guards weren't armed, Tarek said, or "I would have fired on him." Tarek and one other guard were lightly injured by rockets that exploded prematurely, Dempsey said.

"I thought my house was being destroyed, it was such a huge sound," Hamoudi Mutlag, 48, said of the rockets' impact. An Al Rashid maintenance worker, he was asked whether he now feared staying in his house, situated between the firing point and the hotel. "Every place in Baghdad is dangerous now that the Americans are here," he said.

Dempsey said the attackers had welded together a 40-pod launcher that held both 68mm and 85mm artillery rockets. Between eight and 10 struck the hotel, and 11 never left their tubes, he said.

The division commander said the insurgent operation required "some reconnaissance and some rehearsal," and possibly two months' preparation. The device was not sophisticated -- "a science project in a garage with a welder and a battery and a handful of wires" -- but it was effective, he said.

"There is no guarantee we can protect against this kind of thing unless we have soldiers on every block," one of Dempsey's reconnaissance officers, 1st Lt. Brian Dowd, said at the scene.

The general said his troops had to disarm booby-trap explosives attached to the trailer before towing it away.

A coalition official, speaking on condition of anonymity, said the authority later ordered the hotel evacuated indefinitely, its hundreds of guests to be scattered among other lodging places in the so-called "Green Zone," a heavily guarded district along the Tigris River that includes the palace headquarters of the U.S.-led CPA, the offices of the interim Iraqi Governing Council, and the Convention Center housing coalition press relations and other offices.

The formerly government-owned Al Rashid, Baghdad's best-known luxury hotel, was taken over by occupation authorities after U.S.-British forces toppled the Baathist government of Saddam Hussein last April.

The well-planned attack was the second on the hotel, which was hit Sept. 27 by small rockets or rocket-propelled grenades that caused minimal damage and no casualties.

In his brief morning statement, Wolfowitz spoke of "even bigger news" than the hotel attack -- the growing number of Iraqis being trained and equipped "and going out on patrols, fighting these criminals."

The U.S. administration largely blames diehard Saddam loyalists and foreign fighters for the continuing hit-run guerrilla war. But other Iraqis opposed to the U.S. occupation are also believed taking part in the resistance.

At his news conference, Brig. Gen. Dempsey noted the number of attacks had surged beginning in September.

"Why haven't the number of attacks gone down? I don't know the answer to that," he said. The U.S. command is "still trying ... to figure out exactly why that happened."