A large contingent of Iraq's elite Republican Guard headed south in a 1,000-vehicle convoy Wednesday toward U.S. Marines in central Iraq - an area that already has seen the heaviest fighting of the war. In Baghdad, Iraqi officials said two cruise missiles hit a residential area, killing 14.

Intelligence officers with the 1st Marine Expeditionary Force said the Republican Guard units were headed from Baghdad on a route that avoids advancing U.S. Army forces but leads directly to the Marines who have been fighting in recent days around the city of An Nasiriyah.

The advance appeared to signal that the Republican Guard, Saddam Hussein's best trained and most loyal force, was still prepared to take the offensive despite days of allied air strikes and missile attacks on its positions.

In the far south, British forces fought on the fringes of the beleaguered city of Basra, where Iraqi militiamen also faced a local uprising. The first substantial relief convoy reached the Iraqi port of Umm Qasr after weathering a blinding sandstorm in its trip north from Kuwait.

A military source said the U.S. Central Command now had evidence that the Iraqi regime had wired many of the bridges around Baghdad for destruction.

Iraqi officials said the U.S. missile attack in Baghdad killed 14 and injured 30 in the Al-Shaab neighborhood, an area crowded with apartments, auto repair shops and inexpensive restaurants. Associated Press Television News footage showed a large crater in the middle of a street, a child with a head bandage, and bodies wrapped in plastic sheeting in a pickup truck. Hundreds of people stood in front of a damaged building, some shaking fists in the air and shouting.

U.S. Central Command said it had no information about the incident.

''We don't have a report that corroborates that, so I can't confirm it,'' said Brig. General Vincent Brooks. ''We do everything physically and scientifically possible to be precise in our targeting.''

Brooks, at a news briefing in Qatar, also accused the Iraqi government of using its own civilians as human shields for some its military units fighting against U.S. and British troops.

Asked about the Republican Guard movements, Brooks said, ''There have been local positionings and survival positionings, but not serious attacks and we certainly remain, we believe, well in control of the situation at hand.''