The attack in Baghdad came two days after a bombing at the hotel in the city that is serving as the Iraqi headquarters of NBC News.
To the west, in flashpoint Fallujah, U.S. troops killed at least two Iraqi civilians.
The U.S. military said the Fallujah victims had tried to run a checkpoint, but later altered that to say the Iraqis had fired on American soldiers. Wounded survivors said the American fire was unprovoked and came from troops lying in ambush. They said four Iraqis were killed - including two women - the latest in a string of dozens shot by U.S. troops in the Euphrates River town.
The attack on the al-Rashid Hotel, once one of Baghdad's best, now home to U.S. military officers and civilian occupation officials, came at about 6:30 a.m., when someone fired three or four projectiles, apparently from a nearby residential area, U.S. military spokesmen said.
Rounds struck the 14th floor and caused superficial damage, said Charles Heatley, spokesman for the occupation office, the Coalition Provisional Authority. Another round struck a one-story private home near the hotel, leaving a sizable hole. No injuries were reported.
"It did wake us up with a bang," Heatley said. But "we are not unduly concerned about this."
It was, nonetheless, the most daring known attack by resistance fighters on the so-called "green zone," a heavily guarded area of closed-off streets in central Baghdad where U.S. occupation authorities live and work.
The modern, 200-foot-tall hotel stands hundreds of yards from high, earth-filled barriers ringing that section of the zone, site also of the coalition press office at the Baghdad Convention Center and of the headquarters of the U.S.-appointed Iraqi Governing Council.
In other developments:
U.S. troops also unearthed one of their biggest weapons caches to date near the village of Uja, Saddam Hussein's birthplace near Fallujah.
A raid on the farm near Uja was the second in as many days. On a tip, troops dug near a river bank to find 1,000 pounds of explosives used to make the homemade bombs that have killed numerous American soldiers.
The cache also turned up 23 Russian-made surface-to-air missiles; four rocket-propelled grenade launchers and 115 rockets; a mortar and 40 mortar rounds; 1,300 blasting caps and 423 hand grenades, the U.S. m ilitary said.
A spokesman, Lt. Col. George Krivo, said the U.S. military had not immediately determined the nature of the projectiles aimed at the al-Rashid Hotel. Residents of the Salhiya neighborhood west of the complex said a rocket launcher was fired from the middle of the street and was left behind as the attackers fled. Heatley said he was not aware of any arrests.
At the eastern edge of Fallujah, 30 miles west of Baghdad, soldiers of the 82nd Airborne Division manning a position on the eastbound side of the main highway to the capital opened fire on a motorbike and then a following pickup truck headed west into Fallujah, survivers said.
Haidar Jamil, 17, wounded in the left leg and back, told The Associated Press from his hospital bed that his father, mother and grandmother were killed in the pickup. A fourth person, a man on the motorbike, also was killed, said Capt. Taha al-Falahi, security chief of the Fallujah General Hospital. He said at least five other people were wounded, including a child.
Military spokesman Krivo said his reports were that two were killed and four wounded.
CBS News Correspondent Allen Pizzey in Baghdad says, "Whoever is right (about the number of deaths), the end result is the same -- more enemies for the Americans.
An uncle of a victim told Pizzey, "They have come from the other side of the ocean, but they must understand that we will retaliate…our blood will not be spilled in vain."
An initial report from the U.S. military in Baghdad said soldiers fired on a vehicle that ran a checkpoint. Krivo later amended that to say, "There was a van involved. There were shots fired from the van on the traffic control point, and the coalition soldiers returned fire."
Iraqi witnesses said no Iraqis fired on the Americans and there was no checkpoint.
"We were in the pickup truck and close to Fallujah. The Americans were on the other side of the road and as we approached and almost passed them, they fired on us," said Taha Yassin, 29, who was wounded in the arm.
"There will be an investigation," Krivo said.
Since shortly after the lightning defeat of Saddam Hussein's government, Fallujah, a stronghold of Saddam's Baathist party, has been the scene of bloody encounters between American troops and townspeople.
In late April, 82nd Airborne soldiers fired on anti-American protesters in two incidents, killing 18 and wounding 78. On Sept. 12, on the same highway, division soldiers killed eight Iraqi policemen and a Jordanian hospital guard as the police chased a bandit's car.
In another incident Saturday in Fallujah, 22-pound bomb was found planted between the wall of the mayor's office and an adjacent house. Iraqi civil defense forces were summoned to disarm it.
The al-Rashid attack came five days after a car bomb outside Baghdad's U.N. complex killed a suicide bomber and a policeman, and two days after a bomb at a Baghdad hotel housing NBC television staff killed a guard. Heatley said, however, he saw no intensification of attacks.
In the past 60 to 90 days, the daily number of resistance attacks has ranged from "the low teens to the mid-20s," he said. "That remains the same."