The earthquake struck at the end of the afternoon rush hour. The shaking lasted 20 seconds or longer in downtown Cairo and was preceded by a loud roar. Terrified people ran on to the streets, and panicking motorists crashed into one another.
Security sources, who steadily raised their casualty toll as the evening wore on, said they had reports of 163 buildings collapsed or damaged across the sprawling city of 12 million people, one of the most densely packed urban areas in the world.
There are many poor districts where families live packed in badly-built tenement blocks and building collapses are regularly reported. The buildings are rendered even more dangerous by the illegal addition of extra floors by property developers.
Ibrahim el-Himali, an earthquake expert at the government's Helwan observatory, said the shock measured between 5.5 and 6 on the Richter scale, strong enough to damage a city extensively, and had been centred south-west of Cairo.
Officials said that the pyramids, the Sphinx and other ancient monuments apparently escaped damage. The biggest buildings in the city centre, such as the state radio and television centre overlooking the Nile and the 30-storey Ramses Hilton hotel, also survived. But three minarets at one of the city's oldest mosques, the Hanafi, were toppled.
Clouds of dust billowed over the city, which stretches 22 miles from the ancient pyramids of Giza on the west bank of the Nile to medieval slums and new housing developments on the east. Shocks were felt in Alexandria, Assiut in southern Egypt and as far away as Jerusalem, 265 miles away.
Helmeted rescuers with floodlights and mechanical shovels dug through a tangled mass of concrete and reinforcing girders in a desperate hunt for survivors in the ruins of a multi-storey building in the eastern suburb of Heliopolis.
Five people, including a woman and her dead son, were plucked from the twisted rubble of one building.
Distraught, shrieking relatives besieged a hospital in the northern slum district of Shubra el-Khaimah, where doctors said they had registered 34 deaths. Riot police cordoned off the hospital. The doctors said many children had been trampled to death as they fled in panic from their classrooms when the quake struck at 3.10pm.
'The whole school started shaking,' Zainab Ibrahim, a 12-year-old survivor, said. 'I fell on the staircase and all the children stepped on me.'
Agonised parents waited to see whether their children were injured or dead. Chaos ruled the street outside the school. Fights broke out between parents desperate to get the bodies of their children, still dressed in their school uniforms, home for burial, and taxi drivers who refused to take them.
State television said the earthquake struck during a cabinet meeting, and Mr Sedki immediately formed an action group of the ministers of defence, interior, health, local government and supply to deal with the emergency.
Safwat Sherif, the Information Minister, said President Hosni Mubarak cut short a visit to China, part of a five-country foreign tour, to return to Cairo.
In the stricken districts dazed residents stood in alleyways in front of their homes, surrounded by rubble and too frightened to go back in.Reuse content