Anticipating an intense battle, Iraqi civilians packed food and belongings into trucks, buses and cars in a mass exodus from the city's northern and northeastern districts.
Some witnesses described lines of vehicles extending bumper-to-bumper for up to six miles. Many were headed to the province of Diala, northeast of the capital.
Earlier, Health Minister Omeed Medhat Mubarak said hospitals in the capital were swamped with wounded.
At al-Yarmouk hospital, doctors and nurses scrambled to cope with the rush of casualties — including civilians and soldiers from the Republican Guard. The injured could be heard crying in pain. Those too weak to talk pointed to their bloodied bandages and wounds.
"The aggression is not differentiating between civilians and military," Mubarak said.
The hospitals had generators so they could operate despite a power outage that began Thursday night — the first widespread outage in the capital since the war began March 20. U.S. military officials said they had not targeted Baghdad's power grid.
A sustained loss of electricity would mean the disruption of water supply and sewage, which could spread disease at a time of rising temperatures. Some parts of the city of 5 million had no running water.
Some of the injured at al-Yarmouk said they were from the Furat and al-Radwaniyah districts, both close to the airport. People at the hospital said dozens had been killed in the two districts, but that could not be confirmed.
"It was a fierce battle last night and today," said 23-year-old Republican Guard soldier Omar Bahaeldeen Khalil from his hospital bed.
At a sandbagged sentry post in the capital, one guard vowed to resist any U.S. assault.
"We have given allegiance to our leader Saddam Hussein that we will be faithful soldiers," said Abdul Wahid Hidawi. "All they have to do is come to Baghdad to face the real Iraqis and, God willing we will make of them an example to others."
Meanwhile, President Saddam Hussein, in an unannounced TV broadcast, called on Iraqis to fight the invasion. "Let the criminals lose," he said.
Coalition officials have expressed doubt about whether the Iraqi president was alive. In his Friday appearance, his third since a U.S. airstrike aimed at killing him March 20, he made one topical reference: to the March 24 capture of an Apache helicopter in central Iraq.
Soon after, Arab television networks including the Lebanese Broadcasting Corporation, Qatar-based Al-Jazeera and Iraqi television aired footage of a man purported to be Saddam, walking among excited crowds.
Early Friday, the Muslim day of rest, traffic on the streets was about normal, but later some neighborhoods grew unusually quiet and lines at gas stations grew.
Al-Sahhaf, speaking on Saddam's behalf, promised to defeat coalition forces at the gates of Baghdad.
"We are determined, God willing, to defeat them and destroy them on the walls of our capital," al-Sahhaf said.