Army tanks and infantry fought off attacks Friday at Baghdad's international airport, newly seized as a U.S. base just outside Saddam Hussein's capital.

Thousands of Iraqis fled the city, fearing urban warfare.

With U.S. commandos already inside Bagdad, columns of Army and Marine armored vehicles advanced on the city from the South. They met occasionally stiff resistance, battling Iraqi tanks as well as army, Republican Guard and Fedayeen forces.

American forces closed in as Iraqi information Minister Mohammed Saeed al-Sahhaf threatened "very new, creative" martyrdom operations but denied weapons of mass destruction would be involved.

Saddam appeared on television and urged his country to strike advancing troops forcefully.

But the marines reported the surrender of 2,500 members of the Republican Guard, American and British warplanes bombed targets virtually at will for the 16th straight day, and the administration projected increasing confidence.