The United States struck at the Iraqi insurgency hours later, destroying a building in Baghdad in an assault that thundered across the capital. CBS News National Security Correspondent David Martin says the moves are part of the new "get tough" approach of U.S. forces.
The Nasiriyah attack was the deadliest against an American ally since the occupation began and appeared to send a message that international organizations are not safe anywhere in Iraq. It came on the same day the chief U.S. administrator for Iraq went to the White House to put forth proposals on transferring more authority to the Iraqis.
Col. Gianfranco Scalas said 18 Italians were killed: 12 Carabinieri paramilitary police, four soldiers, a civilian working at the base and a documentary filmmaker. A spokesman for the U.S.-led coalition said at least eight Iraqis also died. The bomber -- whose nationality was not known — also died.
The blast wounded 79 people, 20 of them Italians, hospital sources and Italian officials said.
Italians were stunned by their nation's single worst military loss since World War II and its first in the Iraq campaign. At Rome's tomb of the unknown soldier, the green-white-and-red flag rippled at half-staff, and parliament held a minute of silence.
The blast came as a top-secret intelligence report warned that Iraqis were losing faith in the U.S.-led occupation. Meanwhile, President Bush and his top foreign policy advisers held urgent meetings in Washington over how to more quickly transfer power to Iraqis.
T"he CIA's got it right," said CBS News Military Analyst Col. Mitch Mitchell (Ret.), "and their warnings had better be taken seriously, or we're going to have some serious trouble in Iraq.
"We're moving forward glacially. The facts of the real world are that our leadership is not moving quickly enough to get Iraq under control."
In other developments:
Witnesses said the decoy car ran a roadblock in front of a square where the Italian barracks was located. Guards opened fire but as the vehicle sped away, the fuel tanker approached from the opposite direction and rammed into the gate of the building before exploding.
Italian Defense Minister Antonio Martino said the truck, followed by an armored car, approached the compound at high speed. Gunmen inside one of the vehicles opened fire at Italian troops guarding the entrance, he said. The guards returned fire, but the vehicle plowed through the gate, and then exploded, he added.
It was the 13th vehicle bombing in Iraq since Aug. 7, when a car exploded at the Jordanian Embassy in Baghdad, killing at least 19 people. Wednesday's blast from the estimated 650 pounds of explosives collapsed all three stories of the building, gouged a 6-foot-deep crater in front of it, and set fire to parked cars. Secondary explosions from stored ammunition shook the area.